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

Annotations already establish read-only, open-world, idempotent, non-destructive behavior. The description adds meaningful context beyond them: it discloses RFC 9309 matching behavior, returned fields, and a per-call x402 price. It does not cover error handling or rate limits, but it is substantially transparent.

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 compact and front-loaded with the core question, followed by the matching algorithm, return values, and pricing. Every sentence contributes useful information without filler.

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?

There is no output schema, so it is important that the description names the return fields, and it does: allowed/disallowed, deciding rule, crawl-delay, sitemaps, and agent groups. Combined with the annotations and parameter schema, this is complete enough for an agent to invoke the tool correctly.

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?

The url parameter is well explained as the page whose origin's robots.txt is read, but the userAgent parameter has no schema description and is only indirectly referenced in the description as the crawler being evaluated. With 50% schema description coverage, the description adds some meaning but does not fully document userAgent matching or default behavior.

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 states a specific question and operation: fetch /robots.txt and evaluate a URL path for a user-agent under RFC 9309. It clearly distinguishes this from sibling web tools such as web_sitemap by focusing on robots.txt rules, crawl-delay, and agent groups.

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 context of use is clear: checking whether a crawler user-agent is allowed to access a URL path according to robots.txt. It does not explicitly name when not to use it or point to a specific alternative, but the intended scenario is unambiguous.

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