Stéphane Tailland
f49f3ec360
MCP does not report a tool failure as a JSON-RPC error. It reports it as a successful result carrying isError: true, with the reason as text. The node only checked `error`, so it read the failure as data and went on to JSON.parse the sentence "HTTP call failed with status 404" as a product. The throw is what made the webhook answer nothing at all. Now checks result.isError, distinguishes a missing product from any other tool failure, and guards every parse of a payload it did not construct. Through the facade, escalate: true becomes a task in state failed rather than a completed one. Also corrects this file: the earlier note said the run completed in success with every node executing. It did not — that was the wrong execution. n8n's executions list did not return them newest-first as assumed, and the conclusion drawn from it sent the search to the wrong place. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
259 lines
9.9 KiB
JSON
259 lines
9.9 KiB
JSON
{
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"name": "Approvisionnement \u2014 check_availability",
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"nodes": [
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{
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"parameters": {
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"httpMethod": "POST",
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"path": "check-availability",
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"responseMode": "responseNode",
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"options": {}
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},
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"id": "webhook",
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"name": "Webhook",
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"type": "n8n-nodes-base.webhook",
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"typeVersion": 2,
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"position": [
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0,
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0
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],
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"webhookId": "check-availability"
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},
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{
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"parameters": {
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"method": "POST",
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"url": "https://keycloak.sttlab.local/realms/classic-models/protocol/openid-connect/token",
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"sendBody": true,
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"contentType": "form-urlencoded",
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"bodyParameters": {
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"parameters": [
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{
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"name": "grant_type",
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"value": "urn:ietf:params:oauth:grant-type:token-exchange"
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},
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{
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"name": "client_id",
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"value": "classic-models-agent-approvisionnement"
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},
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{
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"name": "client_secret",
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"value": "={{ $env.APPROVISIONNEMENT_CLIENT_SECRET }}"
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},
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{
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"name": "subject_token",
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"value": "={{ $('Webhook').item.json.headers['x-subject-token'] }}"
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},
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{
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"name": "subject_token_type",
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"value": "urn:ietf:params:oauth:token-type:access_token"
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},
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{
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"name": "scope",
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"value": "openid mcp-catalog-audience token-exchange-broker-audience"
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}
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]
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},
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"options": {}
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},
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"id": "exchange-token",
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"name": "Exchange token",
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"type": "n8n-nodes-base.httpRequest",
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"typeVersion": 4.2,
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"position": [
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220,
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0
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]
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},
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{
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"parameters": {
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"method": "POST",
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"url": "https://catalog-dev.sttlab.local/catalog-mcp",
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"sendHeaders": true,
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"headerParameters": {
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"parameters": [
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{
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"name": "Authorization",
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"value": "=Bearer {{ $json.access_token }}"
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},
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{
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"name": "Accept",
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"value": "application/json, text/event-stream"
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}
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]
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},
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"sendBody": true,
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"specifyBody": "json",
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"jsonBody": "{\"jsonrpc\": \"2.0\", \"id\": 1, \"method\": \"initialize\", \"params\": {\"protocolVersion\": \"2025-06-18\", \"capabilities\": {}, \"clientInfo\": {\"name\": \"approvisionnement\", \"version\": \"0.1.0\"}}}",
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"options": {
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"response": {
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"response": {
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"fullResponse": true
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}
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}
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}
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},
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"id": "mcp-initialize",
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"name": "MCP initialize",
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"type": "n8n-nodes-base.httpRequest",
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"typeVersion": 4.2,
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"position": [
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440,
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0
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]
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},
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{
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"parameters": {
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"method": "POST",
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"url": "https://catalog-dev.sttlab.local/catalog-mcp",
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"sendHeaders": true,
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"headerParameters": {
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"parameters": [
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{
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"name": "Authorization",
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"value": "=Bearer {{ $('Exchange token').item.json.access_token }}"
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},
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{
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"name": "Accept",
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"value": "application/json, text/event-stream"
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},
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{
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"name": "mcp-session-id",
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"value": "={{ $json.headers['mcp-session-id'] }}"
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}
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]
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},
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"sendBody": true,
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"specifyBody": "json",
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"jsonBody": "={{ JSON.stringify({ jsonrpc: '2.0', id: 2, method: 'tools/call', params: { name: 'get-product', arguments: { path_productcode: $('Decide the product').item.json.productcode } } }) }}",
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"options": {
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"response": {
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"response": {
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"neverError": true
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}
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}
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}
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},
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"id": "read-stock",
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"name": "Read stock",
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"type": "n8n-nodes-base.httpRequest",
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"typeVersion": 4.2,
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"position": [
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660,
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0
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],
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"alwaysOutputData": true
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},
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{
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"parameters": {
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"jsCode": "// Pull the product code out of the question.\n//\n// Deliberately loose on the part after the underscore: a reference that\n// looks like one but does not exist must reach the catalog and come back\n// as \"no such product\". Rejecting it here would answer \"you named no\n// product\", which is false and sends the caller looking in the wrong place.\n//\n// A regex rather than a model: this agent's critical path is rules, and putting\n// an LLM on it would make a nightly job both slower and less predictable. If the\n// question does not name a product, the agent escalates instead of guessing \u2014\n// an autonomous agent that meets an ambiguity must hand it back, never resolve\n// it on its own.\nconst question = $('Webhook').first().json.body?.question ?? '';\nconst match = question.match(/\\bS\\d+_[A-Za-z0-9]+\\b/);\nif (!match) {\n return [{ json: { productcode: null, question } }];\n}\nreturn [{ json: { productcode: match[0], question } }];\n"
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},
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"id": "decide-the-product",
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"name": "Decide the product",
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"type": "n8n-nodes-base.code",
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"typeVersion": 2,
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"position": [
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220,
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180
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]
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},
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{
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"parameters": {
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"jsCode": "// Turn the MCP reply into a decision.\n//\n// An A2A call returns an answer, not data: the caller learns whether the stock\n// covers what it asked about, and never receives the stock table. That is what\n// keeps this agent from becoming a read proxy onto the catalog domain.\nconst THRESHOLD = 50; // below this, a reorder is due before promising anything\n\nconst decided = $('Decide the product').first().json;\nif (!decided.productcode) {\n return [{ json: {\n answer: 'No product reference in the question. Name one as S10_1949 and ask again.',\n escalate: true,\n }}];\n}\n\nconst item = $input.first();\nif (!item) {\n return [{ json: {\n answer: `The catalog returned nothing for ${decided.productcode}. It may not exist.`,\n escalate: true,\n }}];\n}\nconst raw = item.json ?? {};\nconst body = typeof raw === 'string' ? raw : (raw.data ?? JSON.stringify(raw));\n\n// The endpoint answers as an SSE event, so the JSON sits on a `data:` line.\nconst line = String(body).split('\\n').find((l) => l.startsWith('data:'));\nif (!line) {\n return [{ json: {\n answer: `Could not read the catalog's reply for ${decided.productcode}.`,\n escalate: true,\n }}];\n}\n\nlet rpc;\ntry {\n rpc = JSON.parse(line.slice(5).trim());\n} catch (e) {\n return [{ json: {\n answer: `The catalog's reply for ${decided.productcode} could not be read.`,\n escalate: true,\n }}];\n}\n\n// A JSON-RPC `error` is a protocol failure \u2014 a malformed call, a session gone.\nif (rpc.error) {\n return [{ json: {\n answer: `The catalog refused the read for ${decided.productcode}: ${rpc.error.message}.`,\n escalate: true,\n }}];\n}\n\n// A *tool* failure is not that. MCP reports it as a perfectly successful result\n// carrying `isError: true`, with the reason as text \u2014 so a client that only\n// checks `error` reads a failure as data and tries to parse \"HTTP call failed\n// with status 404\" as a product. Which is exactly what this did.\nconst text = rpc.result?.content?.[0]?.text ?? '';\nif (rpc.result?.isError) {\n const missing = text.includes('404');\n return [{ json: {\n answer: missing\n ? `There is no product ${decided.productcode} in the catalog.`\n : `The catalog could not answer for ${decided.productcode}: ${text}`,\n escalate: true,\n }}];\n}\n\nlet product;\ntry {\n product = JSON.parse(text);\n} catch (e) {\n return [{ json: {\n answer: `The catalog returned something unreadable for ${decided.productcode}.`,\n escalate: true,\n }}];\n}\nconst stock = Number(product.quantityinstock);\nconst available = stock >= THRESHOLD;\n\nreturn [{ json: {\n answer: available\n ? `Yes \u2014 ${product.productname} (${product.productcode}) can be promised: `\n + `${stock} in stock, above the reorder threshold of ${THRESHOLD}.`\n : `No \u2014 ${product.productname} (${product.productcode}) is down to ${stock}, `\n + `below the reorder threshold of ${THRESHOLD}. A reorder is due before it can be promised.`,\n escalate: false,\n}}];\n"
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},
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"id": "answer",
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"name": "Answer",
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"type": "n8n-nodes-base.code",
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"typeVersion": 2,
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"position": [
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880,
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0
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]
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},
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{
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"parameters": {
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"respondWith": "json",
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"responseBody": "={{ JSON.stringify($json) }}",
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"options": {}
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},
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"id": "respond",
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"name": "Respond",
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"type": "n8n-nodes-base.respondToWebhook",
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"typeVersion": 1.1,
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"position": [
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1100,
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0
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]
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}
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],
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"connections": {
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"Webhook": {
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"main": [
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[
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{
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"node": "Decide the product",
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"type": "main",
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"index": 0
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}
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]
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]
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},
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"Decide the product": {
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"main": [
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[
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{
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"node": "Exchange token",
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"type": "main",
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"index": 0
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}
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]
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]
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},
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"Exchange token": {
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"main": [
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[
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{
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"node": "MCP initialize",
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"type": "main",
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"index": 0
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}
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]
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]
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},
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"MCP initialize": {
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"main": [
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[
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{
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"node": "Read stock",
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"type": "main",
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"index": 0
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}
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]
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]
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},
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"Read stock": {
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"main": [
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[
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{
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"node": "Answer",
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"type": "main",
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"index": 0
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}
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]
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]
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},
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"Answer": {
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"main": [
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[
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{
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"node": "Respond",
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"type": "main",
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"index": 0
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}
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]
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]
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}
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},
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"settings": {
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"executionOrder": "v1"
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}
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}
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