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

Annotations only declare the safety profile (destructive, non-idempotent, non-open-world). The description adds real behavioral context beyond that: the key inherits the connection's test/live mode, scopes are optional limits, the secret is returned only once, and the account owner is emailed. Those are exactly the kinds of facts an agent needs before mutating state.

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?

Three tight sentences, front-loaded with the core action and use case, then behavior, then the critical one-time-return caveat. No wasted phrasing.

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, and the description compensates by stating what comes back (the secret, only once) and the side effect (owner emailed). Combined with mode inheritance and scope behavior, an agent has enough to call it correctly; only the absence of explicit sibling routing keeps it from a 5.

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 both parameters are already documented in the schema, setting the baseline at 3. The description adds only a light gloss on scopes ('optional scopes limit it') and does not elaborate on the mode implication or what omitting scopes means beyond 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 ('Create an API key') plus the concrete use case (store in app environment so the app can send texts). It implicitly distinguishes itself from siblings like list_api_keys and revoke_api_key by being the creation path, but never names those siblings 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?

Provides the scenario for use ('an app you are building... so the app can send texts itself'), which is genuinely helpful context. But it gives no explicit when-not guidance or reference to the related siblings (list_api_keys, revoke_api_key) an agent would need to reason about alternatives.

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