List server capabilities (free)

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

Beyond the readOnlyHint annotation, the description adds materially valuable behavioral facts: 'Free — no model call', cacheability by fingerprint, and the exact trade-offs of each detail mode. It also clarifies that include_schemas is an opt-in fallback to codex:// resources, giving the agent a precise mental model of the tool's side effects and cost profile.

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?

The description is long but every sentence earns its place. It front-loads the core purpose and free/no-model-call behavior, then systematically walks through each detail mode and include_schemas. The structure is logical and avoids redundant restatement of the schema.

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 capability-listing tool with an output schema, the description completes the picture: it explains caching, mode differences, fallback behavior, and cost implications. There is no significant missing context that would prevent an agent from selecting or invoking the tool 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?

Even with 100% schema description coverage, the prose enriches both parameters significantly. It explains that detail='full' restates data the agent already holds, detail='contracts' omits tool_details to avoid re-paying for inventory, and include_schemas works in any detail mode. These are semantic insights the schema alone does not convey.

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 immediately states it lists this server's tools, tiers, and result fingerprint. The phrase 'List this server's tools, tiers, and the result fingerprint' is a specific verb+resource pairing that distinguishes it from sibling tools like codex_status, which likely reports status rather than capability inventory.

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 description gives clear usage context: it is free, makes no model call, and supports caching via the fingerprint, which signals when to use it. It also explains when to use include_schemas (resource-blind clients) and warns that detail='full' restates information the agent already holds. However, it does not explicitly name any alternative sibling tools or state a strict when-not-to-use scenario.

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