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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds useful context beyond annotations: it returns only active credentials, is scoped to the current app, maps to a GET operation, and carries the same API/billing/rate limits.

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 compact and front-loaded with the essential return semantics. The endpoint mapping, scope, and API-context notes all add value, though the opening title line and first sentence are slightly 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?

For a simple read-only list operation with one optional parameter and no output schema, the description covers what the tool returns, the scope, and the underlying endpoint. It does not specify the exact response format, but for this level of complexity the description is largely 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 single parameter x_app_id is fully described in the schema with its override behavior and default to the MCP connection header. The description adds no additional parameter meaning, so the baseline of 3 applies because the schema already does the heavy lifting.

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 a specific verb and resource: 'List Google credentials' and 'Returns all active Google Wallet credentials for the current app.' It also pinpoints the exact endpoint, GET /manage-certs/google, which distinguishes it from upload/deactivate credential siblings.

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?

It gives clear context for when to use the tool: retrieving all active Google Wallet credentials for the current app, and notes the certs:manage scope. It does not explicitly contrast with alternatives like uploadGoogleCredentials or deactivateGoogleCredential, but the scope and resource are unambiguous enough.

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