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

Annotations already declare read-only, idempotent, open-world behavior, and the description still adds real substance: the request cost (1 request), what is inspected, the fallback behavior (returns a minimal template when the file is missing), and an honesty caveat that llms.txt is unproven for AI visibility. That last point is behavioral context an agent cannot infer from structured fields.

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 short sentences, each carrying distinct payload: trigger, action plus request cost, and result/fallback behavior. The trigger is front-loaded and there is no 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 the description must convey return values — and it does, covering the existence verdict, format assessment, the missing-file template, and even an interpretive caveat. Nothing an agent needs to invoke or interpret this tool is missing.

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% and the url parameter already documents that any URL on the site or a bare domain is accepted with lookup at the origin. The description's "of the site" echoes rather than extends that, so the baseline 3 applies.

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 pairs a specific verb and resource — fetch /llms.txt, report existence and format compliance — and enumerates the format criteria checked (H1, summary, sections, links). This is clearly a single-file check, distinct from the broader audit_ai_readiness and check_ai_crawlers 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?

"Use when a user asks about llms.txt" gives an explicit trigger condition. It does not name the sibling tools or state when to prefer the broader audit instead, so the routing guidance is clear but not fully comparative.

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