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

Annotations already establish the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description's job is to add context, which it does by disclosing the return shape and the effect of full=true ('includes every post body'). It does not mention response size, pagination, or caching, which would matter for a bulk-read tool, so it stops short of a 5.

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?

Two sentences, zero filler, with the return contents front-loaded and the routing guidance last. Every clause earns its place.

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 no output schema, the description carries the burden of describing the return and does so adequately (index contents, post URLs, full-body variant). A single boolean parameter at 100% schema coverage and a clear sibling distinction leave nothing an agent needs 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 coverage is 100%, so the baseline is 3; the description goes beyond the schema's 'Return /llms-full.txt instead of /llms.txt' by explaining what that difference means in practice ('includes every post body'). That added semantic content justifies a bump above baseline.

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 ('Return the site llms.txt index') and enumerates what it contains: site coverage, every post with its Markdown URL, and other agent entry points. It also names the sibling it is not ('not for finding one post; use search_posts for that'), so an agent can distinguish it without opening the schema.

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?

Gives explicit when-to-use ('whole-site overview or bulk reading') and when-not ('not for finding one post'), and names the correct alternative tool (search_posts) for that case. Nothing is left to inference.

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