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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower, and the description still adds meaningful traits beyond them: values are never returned by this tool or any other, credentials are write-only, and the grouped return shape. That write-only disclosure is the single most decision-relevant fact about this tool and would not be inferable from annotations.

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, no filler, with the scope statement front-loaded and the return-shape detail immediately after. The write-only caveat earns its place because it prevents an agent from attempting to retrieve secret values.

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?

With no parameters, no output schema, and annotations already declaring the safety profile, the description carries the remaining burden well: it explains the grouping, the fields returned, the timestamp, and the write-only constraint. Nothing an agent needs in order to call this correctly is absent.

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 nothing for the description to disambiguate; per the baseline for parameterless tools this sits at 4. No parameter guidance is needed or missing.

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?

States a specific verb (List) and resource (the authenticated customer's stored monitoring credentials), plus exactly what the output contains: provider name, configured key names, and latest updated-at timestamp. It implicitly separates itself from the sibling list_api_test_credentials by narrowing scope to 'investigation agent context' credentials, though it never names that 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?

The description establishes context (the authenticated customer's stored monitoring credentials) so an agent can infer this is the read path for inspecting configured providers, but it never states when to call this versus list_api_test_credentials or the set_investigation_*_credentials siblings, and gives no prerequisites or exclusions.

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