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

Annotations already cover safety (readOnly, non-destructive) and open-world network access, yet the description adds real behavioral context: it fetches a remote file, resolves the URLs that file links to (implying additional outbound requests and latency), and probes for a sibling llms-full.txt. It does not say what happens when llms.txt is missing or unreachable (error vs. findings), which is the main remaining behavioral gap.

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?

A single front-loaded sentence with the action first and the returned artifacts after; every clause names a distinct output, so nothing is filler despite the density.

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?

An output schema exists, so enumerating return values is bonus rather than necessity, and the safety profile is carried by annotations. The definition is nearly complete for a one-parameter remote-check tool; only the failure mode for missing/unfetchable llms.txt is unaddressed.

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?

With a single parameter at 0% schema description coverage, the description must clarify the url argument, and it only partly does: 'a site's llms.txt' hints at a site-level URL but leaves ambiguous whether the agent should pass a bare domain, a homepage URL, or the direct llms.txt URL. The uri format in the schema constrains type but not this choice.

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?

States a specific verb ('Fetch and validate') and resource ('a site's llms.txt'), and enumerates concrete outputs (findings with severity/line numbers, 0-100 score, counts, URL resolution, sibling llms-full.txt). This clearly separates it from generate_llms_txt, which produces rather than checks the file.

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?

Usage is only implied by the verb 'validate' — there is no explicit when-to-use or when-not guidance, and no statement about prerequisites (e.g., whether the site must be publicly reachable or whether to run generate_llms_txt first). An agent can infer intent but not selection criteria against siblings.

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