update_custom_field

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

Beyond annotations (readOnlyHint=false, idempotentHint=true, destructiveHint=false), the description discloses PATCH behavior (only supplied fields change), a significant risk (changing data_type may invalidate existing values), and the recommended safe practice. It does not mention auth requirements or failure modes, but the annotations already carry the core safety profile, and the PATCH detail is valuable additional transparency.

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 compact and front-loaded: the first sentence states the action and scope, the second lists fields, the third warns about a dangerous operation, and the fourth routes to the correct alternative. Every sentence serves a distinct purpose, with no filler or repetition.

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 4-parameter tool with no output schema, the description covers purpose, PATCH semantics, the editable fields, the key danger (data_type change), and the correct sibling tools for value-setting. It does not mention return values, but no output schema exists and the description's job is not to document those. It could add permission requirements or error behavior, but it is substantially complete for the tool's complexity.

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 compensates by naming the editable fields (name, data_type, extra_data) and clarifying that only supplied fields are modified. It does not deeply explain each field's format, but the schema already provides data_type enum and extra_data schema; the description adds the crucial PATCH semantics and the data_type risk warning, which go 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?

The description states a specific verb ('Update'), a specific resource ('ONE custom field definition'), and clarifies PATCH semantics. It explicitly distinguishes itself from setting custom-field values on documents by naming update_document and edit_documents_bulk, and the word 'ONE' contrasts with the bulk sibling edit_custom_fields_bulk.

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 direction: use this tool to update the definition itself, and when the goal is to set values on documents, it names the exact alternative methods ('update_document or edit_documents_bulk with method 'modify_custom_fields''). It also includes a warning about when data_type changes are unsafe, which serves as a conditional usage guideline.

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