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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the description does not need to argue safety. It instead adds genuinely non-obvious behavior: revoked keys are included in the listing, secret values are never returned, and results carry a prefix plus an is_this_key flag identifying the credential being used. The only gap is that magnitude, ordering, or pagination of the key list is not mentioned.

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 short sentences, no filler, and the scoping fact (live and revoked) is front-loaded before the disclosure about secrets. Every clause carries distinct information about what the caller will and will not see.

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?

This is a zero-parameter read with full annotation coverage and an output schema, so the description only needs to set scope and behavioral expectations — which it does, including the important caveat that revoked keys appear and secrets are withheld. Nothing an agent needs in order to call it and interpret the result 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?

The tool takes zero parameters, so the baseline is 4 and there is nothing in the schema for the description to clarify. The mention of prefix and is_this_key is output-side information rather than parameter semantics, which is appropriate and not misleading.

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 states the exact scope of the resource: "Every key on your account, live and revoked," which tells an agent this is a complete enumeration of API keys rather than a filtered lookup. It is clear enough to distinguish from mutation siblings like create_key and revoke_key, though it never explicitly says "list" or names a sibling, so differentiation is by inference rather than statement.

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 implied rather than stated — the agent can reasonably infer this is how you enumerate keys to find an id before revoke_key or use_key, but no sentence confirms that or excludes alternatives. There are no prerequisites, no exclusions, and no named alternative tool, so the guidance is only adequate for a zero-parameter read.

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