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

Annotations only say readOnlyHint=false and destructiveHint=false. The description adds critical non-obvious behavior: the secret is returned only once, it is exposed in conversation context, 2FA elevation is required, 403 signifies expired 2FA session, and profile_id is immutable after creation.

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 operation and the one-time secret warning, then a compact auth/2FA section. Slightly long but every sentence carries a distinct operational fact; no filler.

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 4-param creation tool with no output schema, the description covers the one-time secret handling, 2FA prerequisite chain, failure recovery, and account/auth requirement. An agent has everything needed to call it correctly.

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 parameters are already documented (each including the immutable profile_id note). The description restates the profile_id binding and branding effect but adds no syntax beyond the schema. 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 and resource ('Create a new API key') and immediately clarifies the key differentiator vs siblings like regenerate_api_key and revoke_api_key: the secret is returned only once. The profile_id binding behavior further distinguishes its effect.

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 explicit prerequisites (2FA flow with the exact action_type 'api_key_create'), the ordered steps, the alternative tool names to call (start_2fa, get_2fa_status), and a 403 recovery path. This is rare, actionable when-to-use guidance.

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