Auth whoami

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

The annotations already indicate read-only, idempotent, non-destructive behavior. The description adds useful detail about what is returned and how the behavior differs between instance keys and OAuth tokens (null OAuth-specific fields), exceeding the annotation baseline.

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 description is two concise sentences with no redundant wording. It front-loads the core purpose and then adds relevant conditional detail about token types, all while remaining easy to read.

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?

The description covers the returned fields and the distinction between instance keys and OAuth tokens. It does not mention possible failure modes (e.g., invalid/expired credential), but for a simple identity inspection tool with no parameters and no output schema, it is sufficiently complete.

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 and the schema has no properties, so the baseline score of 4 applies. The description provides no parameter details because none exist, and this is appropriate.

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 clearly states the tool's purpose with a specific verb ('Return') and identifies the resource as the current MCP credential identity. It lists the returned fields (principal email/role, agent name, client, last-used timestamp), making it easy to distinguish from other tools.

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 implies usage: call it to inspect the current credential identity. It does not explicitly contrast with sibling tools like auth_revoke_self, nor does it state when this tool is preferred over alternatives, but the read-only intent is clear.

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