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

Annotations already declare readOnlyHint, idempotentHint and non-destructive, so the safety profile needs no restating. The description adds that it surfaces setup-specific artifacts (webhook URL, suggested names, remaining steps), which is useful, but since an output schema exists this is largely return-value content and no auth or rate-limit context is added.

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 tight sentences with the content enumeration front-loaded and the use case trailing. No filler or repetition.

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 read-only, single-parameter tool with an output schema and full annotation coverage, the description is essentially complete. The enumerated return details are slightly redundant against the output schema, but nothing an agent needs to invoke it correctly 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?

Only one parameter, and schema coverage is 100% with the schema note 'Source id from list_sources'. The description contributes no additional parameter meaning (no format, range, or lookup guidance), so baseline 3 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 gives a specific verb (Fetch) and resource (one source's settings), then enumerates the concrete contents: webhook URL, suggested configuration/topic names, and remaining setup steps. It delineates scope to SES setup, which separates it from general source tools, though it never names a sibling explicitly.

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 states the triggering context clearly: 'Use this to finish or verify SES setup for an existing source.' There is no when-not guidance or named alternative (e.g., update_source), 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.