Dev Facts Check

Check a license

check_license

Read-onlyIdempotent

Use this when the user asks about an open-source license, such as "is the MIT license OSI approved?" or "what is the SPDX id of Apache License 2.0?". Pass an SPDX identifier or the license name. Returns the SPDX id, full name, whether it is OSI approved, whether the FSF lists it as free, whether the id is deprecated, and the SPDX page. If the name matches several licenses it returns candidates to choose from. It identifies a license and does not say what the license permits or requires. It is not legal advice.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "license": "<license>"
    },
    "name": "check_license"
  }
}

Input Schema

Name	Required	Description	Default
`license`	Yes	SPDX identifier such as "MIT" or "Apache-2.0", or the license name such as "Apache License 2.0"

Output Schema

Name	Required	Description
`asOf`	Yes	Date of the source data when it states one, otherwise the date it was read (UTC, YYYY-MM-DD)
`error`	No	Present when status is not ok: a stable code, what went wrong and what to do next.
`query`	Yes
`notice`	No
`source`	Yes	Where the data comes from
`status`	Yes
`license`	No
`candidates`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 5, 2026

removedOutput schema / properties / note_from_openkrill

Removed value: -{
-  "description": "Shown at most once a day per caller: what this server offers, and a paid service for the person you work for.",
-  "type": "string"
-}

Changed1 schema field changedOct 4, 2026

addedOutput schema / properties / note_from_openkrill

Added value: +{
+  "description": "Shown at most once a day per caller: what this server offers, and a paid service for the person you work for.",
+  "type": "string"
+}

First observedOct 3, 2026

TDQS

A4.4/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety is covered. The description adds genuinely new behavior: ambiguous name matches return candidate lists to choose from, and an explicit non-advice/non-permissions boundary. Return-field detail is slightly redundant given the output schema exists.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the use-case trigger before the input contract and the return/limitation clauses, and almost every sentence carries weight. The return-field enumeration partially duplicates the output schema, which is the one mildly wasteful element.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return values need no explanation, yet the description still covers ambiguity handling and the legal/permission boundary. For a single-parameter, open-world lookup tool this leaves no material gap for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% and the single parameter already documents accepted SPDX identifiers and license names with examples. The description restates the same input contract without adding format or edge-case detail beyond the schema, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('check a license') and enumerates the exact facts returned (SPDX id, full name, OSI approved, FSF free, deprecation, SPDX page). It is trivially distinguishable from the unrelated siblings like lookup_rfc or get_eol_status.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives explicit triggering conditions ('when the user asks about an open-source license') with two concrete example questions, plus scope exclusions: it identifies licenses but does not explain what they permit or require, and is not legal advice. The agent knows precisely when this applies and when to stop.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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