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

Annotations cover the safety/state profile (non-read-only, non-idempotent, non-destructive, closed-world), and the description adds genuinely new behavior: the secret is write-only and the response returns only id, name and type. It does not warn that retries create duplicate credentials, but the key lifecycle disclosure is present.

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?

Front-loaded with purpose, then the type-to-fields mapping, then the return contract. Dense but every clause carries information; only minor compression is possible.

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 output schema, the description supplies the return contract (id, name, type) and how the id is consumed by API tests. For a 12-parameter tool with nested objects and conditional requirements, all the critical call-shaping information is present.

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?

Schema coverage is 100%, so the baseline is 3. The description exceeds it by aggregating the per-type conditional requirements (BASIC=username+password, BEARER=token, OAUTH2=tokenUrl+clientId+clientSecret) and stating the constraint that API_KEY needs at least one entry across apiKeyHeaders/apiKeyQueryParams — a rule not present in the schema.

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 and resource: 'Store a reusable auth credential that API tests can use to reach a protected endpoint.' This distinguishes it clearly from sibling create_api_test and from unrelated create_* 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?

Gives clear context for when to use it — provisioning a credential an API test will reference via httpCredentialId/mcpCredentialId. It does not name alternatives (e.g., list_api_test_credentials to reuse an existing one, delete_api_test_credential), so exclusions are absent.

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