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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered. The description adds genuinely new behavioral context beyond the annotations: the exact fields surfaced (label, tags, monthly limit, spend this month) and, importantly, that secrets are never returned. It does not mention pagination or ordering, so not a 5.

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?

A single tight sentence front-loads the resource and scoping, then layers the returned fields and the secrets caveat. No filler, nothing redundant.

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 usefully compensates by naming the returned fields and the secret-exclusion rule. For a zero-required-parameter read tool this is close to complete; only ordering/pagination behavior is unaddressed, which is minor.

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% and the single parameter (include_revoked) is already documented in the schema. The description adds nothing about the parameter, so the baseline 3 applies; there is no gap for it to compensate for.

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 and resource (list API keys) and scopes it precisely to 'your API key and the keys it created', which tells the agent this is not a global key listing. It even enumerates the returned fields. It stops short of naming siblings like create_key/revoke_key/update_key to differentiate, hence 4 rather than 5.

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 only implied: a read operation for viewing your keys. There is no explicit statement of when to use this versus create_key, revoke_key or update_key, and no exclusions or prerequisites. The 'Never returns secrets' clause does imply a boundary (use this to inspect metadata, not to retrieve secret values), which lifts it above a total absence of guidance.

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