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

Annotations already convey read-only, open-world, and idempotent behavior. The description adds meaningful context beyond those annotations: the weighted fields searched (headings ×3, titles ×2, notes ×1), the per-site scoping, and the fact that a site may be indexed on demand. No contradiction with the annotations is evident.

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 deliver purpose, scope, filtering behavior, and a usage recommendation with no filler. The most important information is front-loaded, and the parenthetical weight details are compact and useful.

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?

For a search tool with no output schema, the description communicates the essential returned content: matching docs links and their covering index. It does not describe result ordering, ranking, or exact response shape, but the limit and max_bytes parameters plus the stated output are enough for an agent to call it 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?

With 80% schema description coverage, the schema already explains most parameters. The description adds extra meaning for 'query' by revealing the weighted index fields and for 'site' by clarifying single-site scoping with on-demand indexing, which is not fully captured in 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?

The description states a specific action ('Search the llms.txt indexes') and a concrete result ('get the matching docs links with their covering index'). It also distinguishes itself from reading the whole index, which maps to the sibling llms_index tool.

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?

It explicitly says when to use this tool: 'jump straight to the right page of a docs set instead of reading the whole index,' clearly positioning it against the index-reading sibling. It also explains the 'site' restriction and on-demand indexing, though it does not explicitly spell out when to prefer llms_page.

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