llms.txt index

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower. The description still adds real value beyond them: exact return shape (markdown with title, summary, links by section, trailing file list with sizes), plus the SPA-stub error condition and the 'topic missing means uncovered' semantics. It omits caching/rate-limit behavior, keeping it at a 4.

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?

Opens with the core definition, then layers return shape, usage framing, and edge cases in four dense sentences with no filler. Slightly longer than minimal, but every sentence carries information.

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 correctly carries the burden of explaining the return value (markdown structure and trailing file list) and adds error-path and negative-result semantics. Complete enough for an agent to call and interpret it, though the next-step handoff to llms_fetch is left implicit.

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% for the single 'source' parameter, and the schema already documents accepted forms (domain from llms_list_sources, other domains, full address, https on public names). The description reinforces little beyond the schema, so the baseline 3 applies.

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 concrete verb+resource: fetching the 'Table of contents of a tool's documentation from its domain (llms.txt)'. An agent can tell it apart from llms_search/llms_fetch, though the description never names those siblings, so differentiation is implicit rather than explicit.

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 index is a navigator, not instructions: it's used to pick a page, not to pick actions' clearly frames when to use it, and 'don't guess addresses' adds a usage constraint. It stops short of explicitly routing to llms_fetch for the next step, so it is clear context without full alternative-naming.

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