source_coverage

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

Discloses key behavioral traits: returns matched/missing, does not discover new sources, verify truth, or modify validate_evidence. No annotations present, but description covers needs.

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

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

Three sentences, dense with information, no extraneous text. Front-loaded with purpose.

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

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

Completes the picture by describing return value (matched/missing source types) and limitations. No output schema, but description sufficiently fills gap.

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

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

Schema covers both parameters 100%. Description adds context: clarifies optional category overrides evidence_json.source_category, and explains evidence_json is parsed evidence. Leafs baseline of 3 due to high schema coverage, extra detail earns 4.

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

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

Clearly states the tool diagnoses source coverage of evidence packs, a specific verb+resource. Distinguishes from siblings like validate_evidence by explaining what it does not do.

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

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

Explicitly says when to use ('after collecting evidence') and provides exclusions (does not discover sources, verify truth, change validate_evidence results).

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