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

With no annotations provided, the description fully discloses behavioral implications: reading is recorded against the token, the owner can see the read, and the answer is marked secret with explicit instructions not to copy it. This goes beyond the action itself and addresses audit and secrecy concerns, which is critical for a credential 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?

The description is efficient: the core action and source are stated in the first sentence, followed by crucial behavioral context in two more concise sentences. No wasted words; every sentence adds necessary 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?

For a simple tool with one parameter and no output schema, the description is complete. It explains what the tool does, when to use it, the behavioral consequences, and the secrecy handling. 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?

The schema already describes the only parameter (id) as 'Credential id, from list_credentials.' The description reinforces this source but adds no new meaning. Since schema coverage is 100%, the baseline of 3 is appropriate; the description doesn't need to compensate.

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 description clearly states the specific action: 'Read one credential's value, by the id from list_credentials.' It identifies the resource (credential value), the verb (read), and the source of the id, distinguishing it from siblings like list_credentials. It also implies a security-sensitive read operation.

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?

The description gives explicit guidance on when to call it: 'Call it when you are about to use the value, not to have it on hand.' It implies when not to call it (just for convenience) and notes the cost. However, it doesn't explicitly mention alternatives, though no real alternative exists for reading a credential value.

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