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

Adds real behavior beyond the annotations: the response carries source URL, check date and content hash, and a cache-miss triggers a single on-demand fetch (a side effect not obvious from readOnlyHint/idempotentHint). Note a mild tension with openWorldHint=false, since the on-demand fetch reaches an external site, but this reads as a write-through cache detail rather than a direct contradiction.

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 tight sentences, front-loaded with what is returned before the rationale and the cache-miss edge case. No filler or restatement of the title.

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-value details need not be repeated, and the low-complexity single-param read is well covered including the cache-miss path. It stops short of stating behavior for a domain that is not listed at all, which would be the one remaining gap.

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 there is a single `domain` parameter, so the baseline is 3. The description adds the qualifier 'a listed site', signalling the domain must already be registered, which is modest but useful meaning beyond the schema.

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: it returns the validated, cached llms.txt of a listed site as text plus metadata. An agent understands exactly what comes back. It never names the closely related sibling check_llms_txt, so the boundary between 'read the content' and 'check the file' must be inferred.

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?

'No second fetch needed' and 'works when the publisher blocks automated clients' implicitly tell the agent to prefer this over a direct HTTP fetch, which is genuine context. However, there is no explicit when-not guidance and no routing to alternatives such as check_llms_txt or search_llms_registry for the same domain.

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