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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context beyond this: it categorizes results ('served, missing, gated or 200-with-HTML soft-404'), specifies that it reports which agents ask for missing documents, and discloses the refusal of certain host types. No contradiction with annotations.

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 a single, dense sentence that front-loads the core action and resource list, then adds behavioral detail and an example. It is efficient with no fluff, though the long list of document examples could be trimmed; overall it earns a 4 for structure.

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 complexity (probing 22 documents) and the absence of an output schema, the description effectively explains the result categories (served, missing, gated, soft-404) and that it identifies requesting agents for missing documents. It also notes host restrictions. This is sufficient for an agent to understand what the tool returns and when it may refuse, though it does not detail the exact response format or the 'groups' parameter behavior (which the schema covers).

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 description coverage is 100% (all three parameters have descriptions in the schema), so the baseline is 3. The description does not add new meaning beyond the schema; it merely gives an example (host='example.com') and mentions the tool probes documents, but does not clarify parameter usage or formats beyond what the schema already provides.

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 action ('Probes') and resource (22 specifically named discovery documents like llms.txt, agent card, mcp.json). It differentiates itself from sibling tools (explain_document, validate_agent_card, etc.) by covering a broad set of documents rather than a single one, and the title reinforces the purpose.

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 implies the tool is for checking discovery documents agents and trust indexes ask for, but it does not explicitly state when to use it versus the sibling tools (e.g., validate_agent_card, llms_txt_from_sitemap). It mentions a limitation ('Refuses private, ephemeral and its own hosts') but does not provide clear 'when not to use' guidance or contrast with alternatives.

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