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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description adds a crucial behavioral detail: 'the secret plaintext is never returned.' This goes beyond the annotation by explicitly stating a security-relevant limitation, which is exactly the kind of context agents need. With no output schema, this disclosure is especially valuable.

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, front-loaded sentence delivers the core purpose and the key caveat without any filler. Every word earns its place, making it exceptionally concise and easy to parse.

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 tool with no parameters and no output schema, the description sufficiently covers what it does (list inbound API keys) and the critical limitation (no plaintext secrets). The context is complete for an agent to correctly select and invoke this tool.

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 input schema has zero parameters, and schema description coverage is trivially 100%. Baseline for 0 parameters is 4. The description does not need to add parameter meaning since none 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 starts with a specific verb 'List' and clearly identifies the resource as 'the project's inbound API keys.' It also adds the scope 'metadata only' which distinguishes it from related key-management siblings like create_api_key, revoke_api_key, and rotate_api_key. The purpose is unambiguous and well-differentiated.

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 establishes when to use this tool: whenever you need a project's inbound API key metadata. It also implicitly signals when not to use it (when you want the secret plaintext, as that is explicitly never returned). However, it does not name alternative tools or provide explicit when-not guidance, so it falls short of a 5.

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