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

Annotations already indicate readOnlyHint=false and destructiveHint=false, so the agent knows this is a non-destructive write operation. The description adds minimal behavioral context beyond what annotations provide, only noting that options apply to select/multiselect types. It does not disclose side effects such as permanent creation, uniqueness constraints, or any conditional requirements, so the description adds limited value.

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 short sentences, front-loaded with the main purpose and a helpful parameter hint. Every word earns its place, with no filler or 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 tool has 7 parameters (4 required) and an output schema, but the description doesn't mention uniqueness restrictions on fieldName, whether options are required for select/multiselect types, or what happens on duplicates. It provides the core purpose but leaves these contextual gaps that a user would need to infer or discover elsewhere.

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 100%, with each parameter already described. The description's note 'Use options for select or multiselect fields' reinforces the schema's description for options but doesn't add new meaning. Since the schema already documents everything, the baseline of 3 is appropriate; the description adds little beyond the 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 clearly states the verb 'Create' and the resource 'custom field definition for CRM entities', which is specific and unambiguous. It differentiates from sibling tools like update_custom_field and delete_custom_field by the verb, but doesn't explicitly name alternatives or contrast with them. The additional note about options for select/multiselect adds clarity but isn't strictly needed for purpose.

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 provides no explicit guidance on when to use this tool vs alternatives (e.g., update_custom_field). It implies usage for creating a new field, but doesn't state prerequisites, exclusions, or when another tool would be more appropriate. The only hint is 'Use options for select or multiselect fields', which is more about parameter usage than tool selection.

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