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

Annotations already state the operation is read-only, idempotent, and non-destructive. The description adds valuable behavioral context beyond those annotations: it explicitly assures the agent that the actual key value is never returned ('Never the key itself') and clarifies that only active keys are included.

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 entire description is one focused, front-loaded sentence. It states the resource, scope, returned fields, and a critical privacy guarantee with zero wasted words.

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 zero-parameter read-only list operation, the description is complete: it identifies the resource, scope, and output fields, while annotations cover safety. No output schema exists, but the listed fields sufficiently describe the return value. Nothing essential 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 there is no parameter semantics burden on the description. The baseline of 4 applies here; there is nothing missing because no parameters exist.

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 uses a specific verb ('list') and resource ('API keys'), and specifies scope ('active', 'on this account') and the exact output fields (prefix, label, created, last used). This clearly distinguishes it from sibling tools like create_api_key and revoke_api_key.

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 clearly implies this is the tool for viewing active API keys, while sibling tools like create_api_key and revoke_api_key cover other lifecycle actions. It does not explicitly say 'use this when you need to view keys rather than create or revoke them,' but the distinction is obvious from the verb and resource.

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