{
  "schemaVersion": 1,
  "evaluation": {
    "id": "sequential-thinking-mcp",
    "testedOn": "2026-10-18",
    "coverage": "local-runtime",
    "summary": "Nine checks exercised step validation, branching, revision, process-local history and diagnostic logging. Default stderr contained submitted text; the logging opt-out removed the second fixture string from stderr.",
    "identity": {
      "version": "1.0.0",
      "target": "@modelcontextprotocol/server-sequential-thinking",
      "integrity": "sha512-ykTmeS4Eejs+FESDrD73mDBNYCkb+cCZJ1MWuv7/vwucbVgGfEbBL5HVt2nVw0/vNF8jz+o9sO/WmxxfXt0J6w== (official npm distribution integrity; exact dependency lock retained)"
    },
    "environment": [
      "Windows 11 build 26200; Node.js 24.18.0; @modelcontextprotocol/server-sequential-thinking 1.0.0.",
      "Launch: node <PACKAGES>/@modelcontextprotocol/server-sequential-thinking/dist/index.js in fresh home/config/temp directories. The first process uses default logging; the second sets DISABLE_THOUGHT_LOGGING=true.",
      "Authored strings only; no model reasoning, API call or task-quality benchmark. The host submitted explicit sequence, branch and revision fields."
    ],
    "checks": [
      {
        "id": "initialize",
        "name": "Initialize",
        "method": "{\"method\":\"initialize\",\"params\":{\"protocolVersion\":\"2025-03-26\",\"capabilities\":{},\"clientInfo\":{\"name\":\"ionbin-fixture-eval\",\"version\":\"1.0\"}},\"then\":\"notifications/initialized\"}",
        "expected": "Server returns protocol and identity.",
        "observed": "JSON-RPC result: protocolVersion=2025-03-26; serverInfo={\"name\":\"sequential-thinking-server\",\"version\":\"1.0.0\"}.",
        "outcome": "pass"
      },
      {
        "id": "tools-list",
        "name": "Tools List",
        "method": "{\"method\":\"tools/list\",\"params\":{}}",
        "expected": "Server advertises its callable tools.",
        "observed": "JSON-RPC result: 1 tools; names=sequentialthinking.",
        "outcome": "pass"
      },
      {
        "id": "first-step",
        "name": "First Step",
        "method": "{\"method\":\"tools/call\",\"params\":{\"name\":\"sequentialthinking\",\"arguments\":{\"thought\":\"Fixture plan: compare option A with option B.\",\"thoughtNumber\":1,\"totalThoughts\":2,\"nextThoughtNeeded\":true}}}",
        "expected": "The first structured step is accepted.",
        "observed": "JSON-RPC/tool result: {\n  \"thoughtNumber\": 1,\n  \"totalThoughts\": 2,\n  \"nextThoughtNeeded\": true,\n  \"branches\": [],\n  \"thoughtHistoryLength\": 1\n}",
        "outcome": "pass"
      },
      {
        "id": "branch",
        "name": "Branch",
        "method": "{\"method\":\"tools/call\",\"params\":{\"name\":\"sequentialthinking\",\"arguments\":{\"thought\":\"Fixture alternative: inspect option B first.\",\"thoughtNumber\":2,\"totalThoughts\":3,\"nextThoughtNeeded\":true,\"branchFromThought\":1,\"branchId\":\"fixture-b\"}}}",
        "expected": "A branch can be recorded from an earlier step.",
        "observed": "JSON-RPC/tool result: {\n  \"thoughtNumber\": 2,\n  \"totalThoughts\": 3,\n  \"nextThoughtNeeded\": true,\n  \"branches\": [\n    \"fixture-b\"\n  ],\n  \"thoughtHistoryLength\": 2\n}",
        "outcome": "pass"
      },
      {
        "id": "revision",
        "name": "Revision",
        "method": "{\"method\":\"tools/call\",\"params\":{\"name\":\"sequentialthinking\",\"arguments\":{\"thought\":\"Fixture correction: prior estimate was incomplete.\",\"thoughtNumber\":3,\"totalThoughts\":3,\"nextThoughtNeeded\":false,\"isRevision\":true,\"revisesThought\":1}}}",
        "expected": "A revision completes the synthetic sequence.",
        "observed": "JSON-RPC/tool result: {\n  \"thoughtNumber\": 3,\n  \"totalThoughts\": 3,\n  \"nextThoughtNeeded\": false,\n  \"branches\": [\n    \"fixture-b\"\n  ],\n  \"thoughtHistoryLength\": 3\n}",
        "outcome": "pass"
      },
      {
        "id": "invalid-step",
        "name": "Invalid Step",
        "method": "{\"method\":\"tools/call\",\"params\":{\"name\":\"sequentialthinking\",\"arguments\":{\"thought\":\"Invalid fixture\",\"thoughtNumber\":0,\"totalThoughts\":1,\"nextThoughtNeeded\":false}}}",
        "expected": "Zero is rejected as a thought number.",
        "observed": "Tool result isError=true: MCP error -32602: Input validation error: Invalid arguments for tool sequentialthinking: Too small: expected number to be >=1 at thoughtNumber",
        "outcome": "pass"
      },
      {
        "id": "default-log-content",
        "name": "Default Log Content",
        "method": "{\"operation\":\"Inspect server stderr after the synthetic sequence\"}",
        "expected": "Determine whether default diagnostics contain submitted text.",
        "observed": "containsFixture=true: stderr included the authored string \"Fixture plan: compare option A with option B.\"",
        "outcome": "pass"
      },
      {
        "id": "new-session",
        "name": "New Session",
        "method": "{\"method\":\"tools/call\",\"params\":{\"name\":\"sequentialthinking\",\"arguments\":{\"thought\":\"PRIVATE_SYNTHETIC_STEP\",\"thoughtNumber\":1,\"totalThoughts\":1,\"nextThoughtNeeded\":false}},\"sequence\":\"Start a fresh process with DISABLE_THOUGHT_LOGGING=true.\"}",
        "expected": "A new server starts a fresh sequence.",
        "observed": "JSON-RPC/tool result: {\n  \"thoughtNumber\": 1,\n  \"totalThoughts\": 1,\n  \"nextThoughtNeeded\": false,\n  \"branches\": [],\n  \"thoughtHistoryLength\": 1\n}",
        "outcome": "pass"
      },
      {
        "id": "logging-optout",
        "name": "Logging Optout",
        "method": "{\"operation\":\"Inspect second server stderr\",\"env\":{\"DISABLE_THOUGHT_LOGGING\":\"true\"}}",
        "expected": "The submitted synthetic text is absent from stderr.",
        "observed": "containsFixture=false: stderr contained only the server startup line; PRIVATE_SYNTHETIC_STEP was absent with DISABLE_THOUGHT_LOGGING=true.",
        "outcome": "pass"
      }
    ],
    "findings": [
      {
        "title": "Default logs include supplied step text",
        "basis": "observed",
        "severity": "medium",
        "detail": "The first synthetic step appeared in stderr. With DISABLE_THOUGHT_LOGGING=true, PRIVATE_SYNTHETIC_STEP was absent from the second process stderr. This says nothing about host or client transcript retention.",
        "practicalAdvice": "Set the logging opt-out and check the client logging policy before supplying sensitive details."
      },
      {
        "title": "A structured record is not a reasoning result",
        "basis": "observed",
        "severity": "informational",
        "detail": "The server accepted branch fixture-b and a revision, rejected thoughtNumber=0, and returned history length 1 after a new process started. These are state/schema observations only.",
        "practicalAdvice": "Evaluate the host workflow separately for correctness and cost. Store any required long-term decision record explicitly."
      }
    ],
    "caveats": [
      "The server did not generate or validate the truth of our authored steps.",
      "This reference implementation is not a production quality or intelligence certification."
    ],
    "notTested": [
      "Changes to model accuracy, reasoning quality, token cost or task completion were not measured.",
      "Cross-client isolation, high-volume sessions and host-side transcript retention were not tested."
    ],
    "sources": [
      {
        "label": "Sequential Thinking documentation",
        "url": "https://github.com/modelcontextprotocol/servers/blob/main/src/sequentialthinking/README.md"
      },
      {
        "label": "Current reference-server status",
        "url": "https://github.com/modelcontextprotocol/servers"
      },
      {
        "label": "Implementation",
        "url": "https://github.com/modelcontextprotocol/servers/blob/main/src/sequentialthinking/index.ts"
      },
      {
        "label": "License terms",
        "url": "https://github.com/modelcontextprotocol/servers/blob/main/LICENSE"
      }
    ],
    "reportUrl": "/interface-evaluations/sequential-thinking-mcp.json"
  }
}