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

Beyond annotations (readOnly, openWorld, idempotent, non-destructive), the description discloses return behavior: 'supported, contradicted, or insufficient-evidence with source snippets, or explicit blocked/unreachable/unsupported states.' This gives the agent critical expectations about edge cases and output format, adding meaningful transparency.

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?

The description is two sentences: the first states the core function, the second outlines output states and scope boundaries. No unnecessary words, front-loaded with the most critical information, and every sentence earns its place.

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?

Given the tool's simplicity (two parameters, no nested objects, no siblings), the description covers all critical aspects: claim atomicity, source URL constraints, output states, and non-general scope. The output schema exists, but the description still explains return values, making it comprehensive for agent decision-making.

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 coverage is 100%, with both url and claim fully described in the input schema. The description adds little beyond the schema, merely echoing 'public source URL' and 'atomic' already present. Baseline 3 is appropriate since structured fields carry the semantic weight.

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?

The description clearly states the tool's function: 'Verify one atomic factual claim against one public source URL.' It uses a specific verb (verify) and resource (claim vs. URL), and explicitly excludes broader scope with 'Not a general fact checker,' making its purpose unambiguous even without siblings.

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?

The description provides clear constraints: 'one atomic factual claim' and 'one public source URL,' and explicitly distinguishes from general fact checkers. However, no alternative tools are named, so it lacks explicit 'when-to-use-this-over-that' guidance, though this is mitigated by the absence of siblings.

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