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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds genuine behavioral value beyond that: the content is derived from an existing sitemap and home page, and the result is "ready-to-upload", clarifying that it does not publish to the site itself. It stops short of describing fetch failures or how the sections are chosen.

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. What is produced comes first, the upload instruction second, and the example URL is a compact concrete illustration.

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 return-value burden and does so by naming the file's sections (site name, summary, grouped main pages). Combined with the annotations covering read-only/idempotent behavior and a fully documented single parameter, an agent has everything needed to select and 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?

There is a single parameter with 100% schema coverage, so the schema baseline applies. The description goes slightly beyond it by explaining that the url is consumed together with the site's sitemap to produce the output, contextualising why a home-page URL is required.

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 gives a specific verb ("Build") and resource ("llms.txt"), and even enumerates the produced contents (site name, summary, main pages grouped by section). It is distinct from siblings like generate_schema or generate_schema, though it never explicitly contrasts itself with any of them.

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?

Usage is implied rather than stated: the tool builds an llms.txt for a site, and the description explains where the artifact belongs (site root). There is no when-to-use trigger, no prerequisite (e.g., site must have a sitemap), and no alternative named.

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