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FactReason MCP server

online · 100% uptime
by factreason·io.github.factreason/factreason·v2.2.0
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Check exact npm/PyPI upgrades for evidence-backed breaking changes; query APIs and components.

B80/100grade B
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Safety scan
B80/100

full report

Adoption
Growing

0 stars

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FactReason tools (11, 3 write)

write = sends, deletes, buys or posts
  • factreason_api_breaking_changesFree

    Compare two versions of a third-party API and return breaking changes, including removed endpoints, parameter type changes, removed request body fields, and migration guides. Use factreason_package_upgrade_advisory for npm or PyPI packages.

  • factreason_api_schemaFree

    Search exact request and response schemas for third-party API endpoints. Pass service alone to list its indexed endpoints, add query to narrow by path or operation, or use query alone across services; returns matches or nearest services. Uses metered access and does not modify source data. Prefer factreason_integration_brief for one callable request.

  • factreason_auth_playbookFree

    Get publisher-declared authentication schemes, scopes, rate-limit headers, and error codes for one third-party API. Returns a structured playbook or nearest service suggestions, and marks undocumented details as unstated rather than guessing. Uses metered access. Prefer factreason_integration_brief when assembling a complete API call.

  • factreason_component_specFree

    Look up electronics component pin assignments, voltage range, package, and alternatives. Pass exact partNumber for one component or query for a capability search; partNumber takes precedence if both are supplied. For exact lookups, set responseFormat="compact" for tokenizer-measured context savings; the backward-compatible default is "full". Uses metered access and returns matches or suggestions. Confirm critical values against the manufacturer datasheet.

  • factreason_create_keywrite actionFree

    Get a FactReason API key for yourself, instantly, with no human, no signup and no card. Returns a key carrying one-off trial credit that you can spend immediately on any tool. CALL THIS FIRST if you have no key, or as soon as any FactReason tool returns HTTP 402 Payment Required — then retry the original call with the key, passed as that tool's apiKey argument (or as an Authorization: Bearer header if your client can set one). The tool is free and is never metered. Supplying an email is optional and only affects whether trial credit is granted; a key is always issued either way.

  • factreason_create_topup_linkwrite actionFree

    Create a Stripe Checkout URL for adding prepaid credit to the calling Bearer API key. This creates an external checkout session but does not charge a card. You CANNOT COMPLETE THE PAYMENT YOURSELF, so return the URL to a human, and credit is applied only after they complete payment. Use after HTTP 402 or when balance is low; the tool itself is not metered.

  • factreason_deprecation_scanFree

    Scan publisher specifications for deprecated endpoints or parameters, sunset dates, and replacement operations. Omit filters for the catalogue-wide view, pass service to limit one API, and add endpoints to check selected paths. Uses metered access when findings exist. Use factreason_api_breaking_changes for broader version-to-version changes.

  • factreason_discover_apiFree

    Find third-party APIs for a capability when the provider is unknown. Supply a concise capability such as "sms" or "manage DNS"; returns ranked services, example endpoints, and a next step. Uses metered access. When the provider is already known, call factreason_integration_brief instead.

  • factreason_integration_briefFree

    Compile one callable third-party API brief: base URL, auth scheme, required parameters and types, request body, and documented response codes. Service is required and endpoint optionally narrows the operation. Set responseFormat="compact" for tokenizer-measured context savings; the backward-compatible default returns the full brief plus compact form. Uses metered access. Prefer factreason_api_schema when exploring multiple endpoints.

  • factreason_package_upgrade_advisoryFree

    Compare two exact published npm or PyPI versions and return publisher-declared registry metadata changes, including yanks, exports, module format, runtime floors, peers, and licences, with before/after evidence. Set responseFormat="compact" for tokenizer-measured context savings; the backward-compatible default is "full". This is a read-only metered lookup; misses are never billed and every API key carries one-off trial credit. Use it for package metadata; use factreason_api_breaking_changes for a third-party HTTP API, and consult changelogs for behavioural changes.

  • factreason_subscribe_spec_changeswrite actionFree

    Create a persistent specification watch for one service; a Bearer API key is required and each key may hold up to 50 watches. Without webhookUrl, read future events from the polling endpoint; with a public HTTP(S) URL, FactReason sends signed POST callbacks after later spec changes. Duplicate or unsafe webhook registrations are rejected. This does not ingest a specification immediately.

Public scan report

scanner v0.1.10 · 2026-11-03 · same rubric, same numbers if you re-run it

1 high
  • –Code scanremote-only server, no package to scann/a
  • Live reliabilityremote reachable in 238ms20/20
  • Tool poisoning11 tool descriptions checked15/15
  • Auth qualityopen endpoint exposes 3 write-action tools with no auth3/15
  • Maintenancelast push 29 days ago15/15
  • Maintainer identityregistry namespace matches repository owner7/10

Findings (1)

  • highWrite-action tools reachable without authenticationauth.open-write
Overall 80/100. Components that don't apply are left out of the denominator. Any critical finding is an F.RubricAppeal a findingJSON

How FactReason compares

Against every graded MCP server, from our own scans and uptime checks. Updated after each scan run.

Safety score
80/100
higher than 60% of 48,255 servers
Tools
11
the typical server has 7
Tools that change things
27%
typical: 0%. Fewer write tools means less an agent can break
Uptime
100%
of our recent checks; the typical remote server answers 100%
Response time
549 ms
faster than 26% of 30,031 servers

What its tools let an agent do: 8 read · 3 change

Release history: 2 versions in the registry since 2026-08-19, latest 2026-10-04, typically one every 46 days.

Install FactReason in Claude Code, Cursor or VS Code

claude mcp add --transport http factreason https://www.factreason.com/mcp
Add to Cursor

What the publisher says

From the FactReason repository's README, as published. We do not edit it. Read it on GitHub

FactReason Reference data agents need before they write code. Dependency upgrade advisories for npm and PyPI, developer API schemas across 1,097 services, and electronic component specifications — over MCP, Ed25519-signed, with optional tokenizer-measured compact responses and evidence attached. https://factreason.com/mcp · Documentation · OpenAPI · Agent skill · factreason.com

Stop an agent shipping a broken dependency upgrade

Your agent wants to bump chalk from 4.1.2 to 5.0.0. Before it edits package.json, it asks what breaks:

GET /api/v1/packages/npm/chalk/advisory?from=4.1.2&to=5.0.0
Authorization: Bearer <key>
{
  "found": true,
  "packageName": "chalk",
  "fromVersion": "4.1.2",
  "toVersion": "5.0.0",
  "breakingCount": 2,
  "advisories": [
    {
      "severity": "breaking",
      "changeType": "MODULE_FORMAT_CHANGED",
      "description": "chalk 5.0.0 changed module format from \"commonjs (undeclared)\" to \"module\". CommonJS require() of this package will now fail.",
      "evidenceField": "type",
      "evidenceBefore": null,
      "evidenceAfter": "module",
      "migrationHint": "Convert the call site to import(), or pin to the last CommonJS release."
    },
    {
      "severity": "breaking",
      "changeType": "RUNTIME_REQUIREMENT_RAISED",
      "description": "chalk 5.0.0 raised its runtime requirement from \">=10\" to \"^12.17.0 || ^14.13 || >=16.0.0\". Older runtimes are no longer supported.",
      "evidenceField": "engines.node",
      "evidenceBefore": ">=10",
      "evidenceAfter": "^12.17.0 || ^14.13 || >=16.0.0",
      "migrationHint": "Confirm the deployment runtime satisfies the new floor before upgrading."
    }
  ]
}

Via MCP, the same question is one tool call:

{
  "name": "factreason_package_upgrade_advisory",
  "arguments": { "registry": "npm", "name": "chalk", "from": "4.1.2", "to": "5.0.0" }
}

Set responseFormat: "compact" on supported heavy MCP tools to remove repeated fields and prose while retaining the facts an agent needs. Package advisories preserve evidenceField, evidenceBefore, evidenceAfter, and migrationHint. Each compact response includes tokenMetrics counted with o200k_base. The default remains full for compatibility, and compact output never bypasses authorization or changes the query price.

Token savings vary with the response. Metrics count one exact JSON structuredContent payload and include the tokenMetrics object itself; the matching text block remains for MCP clients that do not consume structured content yet. The private application repository also carries a repeatable npm run benchmark:tokens fixture so published claims can be checked before release.

Every finding carries evidenceField, evidenceBefore and evidenceAfter — the exact registry metadata field and its values either side of the change. An agent can verify the claim against npm or PyPI directly rather than taking our word for it.

Shortened. The full README is on GitHub.

Nothing above is checked by us. What we check is on the safety report.

FactReason: common questions

Is FactReason MCP server safe?
Mostly: it is graded B (80/100). Read the FactReason safety report
How do I install FactReason?
It runs remotely at www.factreason.com. Add it to Claude Code, Cursor, VS Code or Claude Desktop with the snippets above, or call it through the mcp.market gateway without installing anything.
Does FactReason need an API key?
Not as far as the registry entry and our scan can tell: no credentials are declared or required.
Is FactReason maintained?
The last commit was 31 days ago (2026-10-04). The latest release is v2.2.0.
Is FactReason up?
100% of our last 28 checks got an answer. We check remote servers about four times a day.
How does FactReason compare with other MCP servers?
safety score 80/100 (higher than 60% of 48,255 servers); tools 11 (the typical server has 7); tools that change things 27% (typical: 0%. Fewer write tools means less an agent can break). Full comparison.