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

No annotations are provided, so the description carries the full burden. It discloses that it is a write to a sensitive credential vault, requires proof of npub ownership, and merges without affecting other fields. It does not detail auth beyond npub proof or rate limits.

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 five sentences, each adding distinct information: action, merge behavior, examples, cost, and requirement. It is front-loaded with the main purpose and contains no extraneous content.

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?

Given the complexity (4 required params, no nested objects, output schema exists), the description covers what the tool does, when to use it, and key behavioral notes. It does not discuss error handling or conflict resolution, but is largely sufficient.

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%, baseline 3. The description adds value by explaining the merge behavior ('Merges into existing stored credentials without affecting other fields') and providing usage context, which goes beyond the schema parameter descriptions.

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 'Add or update a single patron credential field,' specifying the verb and resource. Among sibling tools like 'weather_delete_patron_credential' and 'weather_get_patron_credential_fields', this differentiation is clear.

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 provides usage context with examples: 'Useful for setting an account identifier after OAuth, changing a default brain, etc.' and notes it is free. However, it lacks explicit when-not-to-use or direct comparisons to sibling alternatives.

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