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

Annotations already declare readOnlyHint, idempotentHint and non-destructive behavior, so safety is covered. The description adds meaningful context beyond that: 'Secret material is never included' discloses a security-relevant return constraint, and the field list signals what the caller receives. It stops short of describing pagination or empty-result behavior.

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 short sentences with zero waste. The return-shape constraint is front-loaded and the follow-up action is stated second, so the most important information is not buried.

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 zero-parameter, read-only list tool with no output schema, the description supplies the return fields (id, name, type) and the secret-exclusion guarantee, which is what an agent needs to call and consume it. Pagination/limits are not mentioned, a minor omission.

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 to document and the baseline is 4. The description does not need to compensate for any parameter gap.

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 states a specific verb and resource ('List your stored credentials') and narrows scope to three fields (id, name, type). The second sentence ties it to API tests, but it never explicitly distinguishes itself from the similarly named sibling list_investigation_agent_context_credentials, leaving a small ambiguity an agent must resolve from the tool name.

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?

'Use the returned id to attach a credential to an API test' implies the workflow this tool feeds into, but gives no explicit when-to-use guidance or when-not-to-use/alternative comparison against the other credential-listing and credential-mutating siblings. Usage is inferred rather than stated.

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