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

The destructiveHint annotation already signals mutation, but the description adds valuable context that only provided fields are changed, preventing assumptions about full replacement. It does not describe response format or permission requirements, but this is partially covered by the annotation.

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 two sentences plus a REST endpoint reference. Every word is purposeful, front-loaded with the action, and free of redundancy.

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?

The description adequately covers the main behavior and partial-update semantics for an update tool with a well-covered schema. It lacks explicit return value information, but this is not critical given the absence of an output schema and the straightforward nature of an update operation.

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 covers all 11 parameters with descriptions, so the description does not need to add parameter-level detail. The description adds no extra parameter semantics beyond the schema, warranting the baseline score of 3.

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 tool's action: 'Update fields on an existing contact.' This specifies the verb (update) and resource (existing contact), distinguishing it from sibling tools like create_contact, get_contact, and update_ticket.

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 implies usage context by saying 'existing contact' and emphasizes partial updates ('Only provided fields are changed'), which guides when to use it. However, it does not explicitly mention alternatives or when not to use it, so it falls short of a 5.

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