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

Annotations already provide readOnlyHint=false, destructiveHint=false, and idempotentHint=true, establishing the safety profile. The description adds value by listing exactly which fields can be updated, which clarifies the scope without contradicting the annotations.

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 a single, front-loaded sentence that states the action and enumerates the affected attributes concisely. Every word contributes meaning, with no redundancy or filler.

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?

With a fully documented schema, a present output schema, and annotations covering idempotency and non-destructiveness, the description provides sufficient context for an update tool. It could mention potential side effects of changing field type (e.g., impact on existing values), but this is not strictly necessary given the structured data.

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 input schema has 100% coverage with descriptions for all six parameters, including definitions for fieldLabel, fieldType, options, isRequired, sortOrder, and definitionId. The description summarizes these semantic fields but adds no new detail beyond the schema, so the baseline score of 3 is appropriate.

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 uses the specific verb 'Update' with the resource 'custom field definition' and enumerates the updatable attributes (label, type, options, required flag, sort order). This clearly distinguishes it from sibling tools like create_custom_field, delete_custom_field, and get_custom_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?

The description implies usage for modifying an existing custom field, as it requires a definitionId and refers to updating attributes. However, it does not explicitly state when not to use it or mention alternatives, so it falls short of a full 5.

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