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

Annotations already declare read-only, idempotent, open-world behavior, yet the description adds materially new context: a free tier of 10 calls/day, a $0.002/call fallback, two payment paths (x402 via params._meta or HTTP, and X-API-Key credits), and the hosting provider. Cost and auth mechanics are exactly the kind of operational detail 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?

Purpose is front-loaded in a single dense clause followed by a compact payment/access sentence; nothing is redundant. The bracketed provider tag at the end is slightly noisy but small.

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 return values need no explanation, annotations cover the safety profile, and the description still supplies the validation rules, optional behavior, cost, and auth path. An agent has everything needed to decide and invoke 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?

Schema coverage is 100%, so url, text, and checkLinks are already documented in the schema, including the "up to 8 links" limit. The description only echoes the optional link check and the site-level URL framing, adding little semantic value beyond what the schema 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?

States a specific verb and resource ("Check a site's /llms.txt against the llmstxt.org format") and enumerates the exact criteria checked: H1, summary, sections, link entries with notes. This distinguishes it from siblings like broken_links or json_schema_validate, which validate different artifacts.

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 when to use it (validating an llms.txt file) and notes an "optional link check" mode, but never states when to prefer it over alternatives or what prerequisites exist beyond payment. No explicit when-not guidance or named alternative is given.

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