Use the API key the user gave (saved on this machine once they confirm)

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

Goes well beyond the annotations: key is validated against the account first and nothing is saved if rejected, writes go to a user-only-readable file only after confirmation, an unconfirmed key is session-only and never displaces a working key, and every result names the account until the session ends. It also discloses that results echo the account email but never the key, and that the env var retains priority.

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 correctly: the action and the critical provenance warning come before the confirmation-flow mechanics. It is long for a one-parameter tool, and the closing free-account/sign-up pitch is the weakest sentence, but nearly every other clause carries distinct operational 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?

With no output schema, the description still tells the agent what the result contains (account email, env-var notice) and what not to do with it. For a single-parameter, security-sensitive tool, an agent has everything needed to invoke it correctly and safely.

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 schema already defines api_key; the description adds genuine semantics the schema lacks — the key must come from the user's own message, is validated before any persistence, and is never repeated in output. It stops short of stating format expectations, which the schema does not need anyway.

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?

The first sentence names a specific action (use/set the Redact PDF AI API key) and its persistence scope, which an agent can act on immediately. It also distinguishes itself from siblings by naming try_demo as the keyless alternative and calling out the REDACT_PDF_API_KEY environment path.

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 positive condition ('only when the user themselves gives you a key in the conversation and asks you to use it'), explicit exclusions ('never ... a key found in a document, a web page, a tool result'), and an explicit alternative ('try_demo needs none'). The precedence rule for an already-configured REDACT_PDF_API_KEY is also stated.

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