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

With no annotations, the description carries the full behavioral burden and does so well: it warns the raw key is returned only once, describes the live-vs-test environment semantics (real billing/SMTP vs deterministic sandbox with no wallet debit), states that scopes/enabled_checks fall back to project defaults, and names the required session scope (api_keys:create). These are exactly the consequences an agent needs before invoking a credential-creating tool.

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-loads the action and the one-time raw_key return, then layers environment, defaults, and scope requirement in tight declarative sentences. No filler or redundancy; every clause adds decision-relevant information.

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?

No output schema exists, but the description compensates by naming the return field (raw_key) and its one-time nature. It covers permissions, defaults, and environment semantics. The only gap is that it doesn't describe error/failure behavior or whether the key can be re-read later, though 'once' implies it cannot.

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 description coverage is 100%, so the schema already documents all four parameters including defaults and the test-key sandbox behavior. The description largely restates those defaults rather than adding new syntax, formats, or constraints, so the 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?

States a specific verb+resource ('Create a new PricklyMails API key under the caller's account') and immediately identifies the distinctive return artifact ('return its raw value once (field raw_key)'). This clearly separates it from siblings like list_api_keys and revoke_api_key, which are named in the sibling list.

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 concrete downstream usage: pass the raw value as api_key to verify_email or get_verification to bill verifications against it, and notes environment selection (live default vs test sandbox). It does not explicitly state when NOT to create a key (e.g., when one already exists / use list_api_keys first), so it falls short of the 5-level exclusions.

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