update_merge_field

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

Discloses that 'Choices are replaced entirely (old choices are lost),' which is a destructive-like behavior beyond annotations. Also mentions 404 error for invalid merge_id. Annotations have destructiveHint: false, which is consistent since this is an update, not deletion. Provides useful context beyond structured fields.

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?

Well-structured with clear sections: purpose, caution, error info, args, returns. Front-loaded with main action. Some redundancy in args section (e.g., 'Only provided fields are updated' could be implicit), but overall efficient and easy to parse.

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 7 parameters, 0% schema coverage, and no enums, the description covers all aspects: parameter semantics, constraints, error handling, and return format (JSON with fields). Output schema exists but description adds valuable detail. No gaps for an update 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?

With 0% schema description coverage, the description fully carries parameter meaning. It explains all 7 parameters, including format of list_id (10-char alphanumeric), merge_id (numeric string), and the comma-separated format for choices, plus their constraints (choices ignored for non-dropdown/radio types). This goes far beyond the bare schema.

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?

Description clearly states 'Update a merge field's name, default value, required flag, or dropdown/radio choices.' This verb+resource combination is specific and distinct from siblings like create_merge_field and delete_merge_field.

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?

Explicitly states not to use for changing field type or tag, instead directing to delete_merge_field then create_merge_field. Also provides sources for list_id and merge_id. However, lacks explicit when-not conditions for other scenarios like partial updates vs. full replacement.

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