FactReason

Measured conclusion: Deep-tested. L2 outcome: tools_ok.

Check exact npm/PyPI upgrades for evidence-backed breaking changes; query APIs and components.

Add to your agent

Copy this into your MCP client config:

{
  "mcpServers": {
    "FactReason": {
      "url": "https://www.factreason.com/mcp",
      "transport": "streamable-http"
    }
  }
}

Measured tools (11)

• factreason_package_upgrade_advisory read-only

  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.

  Parameters:

  • registry (required) — string — Registry containing both package versions
  • name (required) — string — Exact package name, e.g. "chalk" or "urllib3"
  • from (required) — string — Exact currently installed version, e.g. "4.1.2"
  • to (required) — string — Exact target version, e.g. "5.0.0"
  • apiKey — string — Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.
  • responseFormat — string — Use compact to remove repeated prose and fields while retaining evidence; full preserves the legacy response contract

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• factreason_api_breaking_changes read-only

  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.

  Parameters:

  • service (required) — string — Third-party API service, e.g. "Stripe" or "OpenAI"
  • apiKey — string — Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.
  • toVersion — string — Optional exact version being evaluated
  • fromVersion — string — Optional exact version currently targeted

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• factreason_api_schema read-only

  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.

  Parameters:

  • query — string — Optional endpoint path or operation, e.g. "payment_intents"
  • apiKey — string — Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.
  • service — string — Optional service filter, e.g. "Stripe"

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• factreason_integration_brief read-only

  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.

  Parameters:

  • service (required) — string — Third-party API service, e.g. "Stripe" or "Twilio"
  • apiKey — string — Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.
  • endpoint — string — Optional path or operation fragment used to select one call
  • responseFormat — string — Use compact for the callable facts only; full preserves the legacy brief response

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• factreason_discover_api read-only

  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.

  Parameters:

  • capability (required) — string — Capability to search for, e.g. "send an SMS" or "charge a card"
  • apiKey — string — Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• factreason_create_key

  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.

  Parameters:

  • email — string — Optional contact address for the key owner. Improves the chance of receiving trial credit and lets the operator reach you about corrections. Never send a human's address without their agreement.

  Hints: read-only no · destructive no · idempotent no · open-world no

• factreason_create_topup_link

  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.

  Parameters:

  • amountUsd (required) — number — Credit amount in USD; common blocks are 10, 50, and 200
  • apiKey — string — Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.

  Hints: read-only no · destructive no · idempotent no · open-world yes

• factreason_component_spec read-only

  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.

  Parameters:

  • query — string — Free-text capability search, e.g. "3.3V ARM MCU with SPI"
  • apiKey — string — Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.
  • partNumber — string — Exact part number, e.g. "STM32F401RE"
  • responseFormat — string — Use compact for an exact part lookup; full preserves the legacy data response

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• factreason_deprecation_scan read-only

  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.

  Parameters:

  • apiKey — string — Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.
  • service — string — Optional service filter, e.g. "Stripe" or "Twilio"
  • endpoints — array — Optional endpoint paths to check within the selected service

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• factreason_auth_playbook read-only

  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.

  Parameters:

  • service (required) — string — Third-party API service, e.g. "Stripe", "Twilio", or "Cloudflare"
  • apiKey — string — Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• factreason_subscribe_spec_changes

  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.

  Parameters:

  • serviceName (required) — string — Service name to watch, e.g. "Stripe" or "SendGrid"
  • apiKey — string — Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.
  • webhookUrl — string — Optional public HTTP(S) URL for signed change callbacks; omit to poll

  Hints: read-only no · destructive no · idempotent yes · open-world yes

Publisher website Repository

Measured by MCPYP probing. Untested fields are omitted, never estimated. Listing is always free; MCPYP never proxies calls or stores user tokens.