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

Goes well beyond the readOnlyHint annotation: it discloses the URL guard and size cap, the exact price and payment rails (x402 on Base/Solana/Arc), and that failed calls are not charged. That is precisely the paid-call context an agent needs before invoking.

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?

Return shape is front-loaded in the first clause, then behavioral constraints, then pricing. It is a single dense paragraph that stays on topic, though the pricing sentence could be trimmed slightly.

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?

With an output schema present, the description need not enumerate return fields, yet it summarizes them anyway. Cost, guardrails, and failure charging are all covered, leaving nothing an agent needs missing before calling.

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% with a single required url parameter, so the schema carries the parameter burden. The description adds the semantic constraint that the URL is read under the same guard/cap as page tools, which is meaningful but not additional per-parameter syntax.

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 resource (llms.txt / llms-full.txt) and exactly what is returned: parsed title, summary, sections with links, and the size of llms-full.txt. 'Whether a site publishes' frames the tool as an existence check plus parse, which is distinguishable from siblings like robots, sitemap, and read.

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 phrase 'reads the site itself, through the same URL guard and size cap as the page tools' implies the context (LLM-oriented site discovery) but never states when to prefer this over sitemap or robots, nor any prerequisite about which sites actually publish llms.txt. Usage is inferable, not explicit.

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