update_contact

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

With no annotations provided, the description carries the full burden of disclosing behavior. It explains the replace vs. merge semantics, how to remove values by setting an empty list, and provides a concrete example of the fields_json format. This gives meaningful insight into the tool's behavior, though it does not mention irreversibility or permission requirements.

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 well-structured with an 'Args' section, parameters clearly listed, and a concise example. Every sentence adds value, explaining the JSON format and edge cases (emptying a field). No fluff or repetition is present, making it appropriately sized for the tool's complexity.

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 that an output schema exists (per context signals), the description need not explain return values. It comprehensively covers all input parameters, their formats, and behavioral nuances such as replace vs. merge and removal of values. This is sufficient for an agent to correctly invoke the tool.

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 0%, so the description must compensate. It provides detailed semantics for all three parameters: contact_id is identified as the Nimble contact ID, fields_json is explained with a format and example, and replace is defined with true/false behavior. This significantly exceeds the schema's basic type information.

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 'Update an existing contact's fields' with a specific verb and resource. This distinguishes it from siblings like create_contact, delete_contact, and list_contacts by virtue of the 'update' operation, even though no explicit comparison is made.

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 when modifying existing contacts, but does not explicitly state when to use this tool versus alternatives like create_contact or replace_tags. No exclusions or alternative recommendations are provided, leaving the guidance at an implied level.

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