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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), yet the description still adds real behavioral context beyond them: 'Keyless' (no auth needed), 'No charge' (billing), plus concrete error codes (INVALID_ARGUMENT for empty intent, UNAUTHORIZED for bad bearer). That is auth, cost and failure-mode disclosure that the structured fields do not carry.

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?

Purpose is front-loaded in the first sentence, followed by routing, cost/auth flags, return shape and errors in dense fragments. Every clause earns its place, though the telegraphic fragment style ('Keyless. No charge. Read-only.') is slightly choppy rather than smoothly structured.

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 two-parameter resolver, the description covers purpose, routing, auth/cost, returns and error modes, and an output schema exists so return values need not be fully explained. Nothing an agent needs to select or call this correctly is missing.

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%, so both parameters (intent, requirements) are already fully documented, establishing the baseline of 3. The description adds only the 'intent is empty' error case and otherwise restates what the schema provides, so it does not meaningfully exceed baseline.

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 specific verb ('Match') and resource ('capability key') with the modality ('natural language'). It explicitly distinguishes itself from the sibling hydracept_capabilities, so an agent can route between them without opening either schema.

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 an explicit when-to-use ('use when the key is unknown') and a named alternative with its own selection condition ('use hydracept_capabilities when you already have a key or need the catalog'). This is exactly the when/when-not/alternative pattern.

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