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

Goes well beyond the annotations (readOnly=false, destructive=false, idempotent=false), which only flag this as a non-destructive write. The description adds that it is a SECRET-CREATING write requiring confirmation, that scopes can only be inherited from the calling dashboard key, that team-management and client-portal permissions are never copied, and that brand-limited keys cannot create keys — these are non-obvious authorization and inheritance rules an agent could not infer.

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 safety warning before the permission detail, and every sentence carries a real constraint. Some sentences (the scopes/team-management sentence) are dense enough that a reader has to parse carefully, which keeps it just under top marks.

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?

There is no output schema, and the description implies rather than states that the response contains the secret key material and whether it is shown only once. Otherwise the authorization model, scope inheritance, and confirmation requirement are covered thoroughly for a six-parameter mutation.

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 every parameter already has documented semantics including the scopes enum items and the confirm constant. The prose restates the workspace_client_id brand-limiting rule and the scope-inheritance rule rather than adding new detail, so the schema baseline of 3 applies.

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 posterly API key for the authenticated user") and immediately scopes who can do it (OAuth and managed assistant tokens cannot mint keys), which separates it from sibling credential tools like delete_api_key or manage_oauth_client. It stops short of naming a sibling as an alternative, so it lands at 4 rather than 5.

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?

Explicit gate: "only use after explicit user confirmation," which the schema's confirm constant reinforces. It also tells the agent when to omit workspace_client_id (workspace-wide key) and states a precondition that a brand-limited key cannot create keys. No named alternative tool, but the when-to-use conditions are clear.

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