list_repos

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

Annotations already declare readOnlyHint and closed-world behavior, so the description only needs to add context beyond them. It does so by disclosing the result set is limited to repos already indexed and that entries are tied to a specific indexing commit. It says nothing about empty results or staleness of the index, which keeps it below the top band.

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, no filler. The result content is front-loaded and the workflow instruction follows, so an agent can act on the first clause alone.

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 no-argument tool with an output schema and read-only annotations, the description covers everything needed to decide to call it and to know what comes back. Return-field detail is legitimately delegated to the output schema.

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?

The tool takes no parameters, so the baseline of 4 applies; there is no input semantics for the description to explain. The description correctly spends its space on output scope instead of inventing parameter detail.

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?

Names a specific verb and resource (list repositories) and states what each entry carries: size, languages, and the commit it was indexed at. The scope phrase 'indexed so far' separates it from index_repo, which is the tool that adds 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?

Gives explicit ordering guidance ('Use this first') and a concrete reason: to obtain the repo names that the other tools require. It does not name a competing alternative or state when-not to call it, but for a zero-argument entry-point tool that guidance is sufficient.

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