Rename a custom field or change its dropdown options. Cannot change entity_type or field_key (create a new field if you need either). Cannot change type (data integrity).
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | Custom field UUID. Get from custom_fields_list. | |
| name | No | New human label. | |
| options | No | For type=select fields only: replace the allowed-values list. | |
| position | No | Order in the field list (lower = first). |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden. It usefully discloses immutability constraints and a data-integrity rationale, but it does not explain side effects of replacing dropdown options on existing saved values, whether the update is partial, or what the tool returns.
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?
Three short sentences are front-loaded with the primary action and immediately state constraints; there is no filler or repetition. Every sentence contributes useful selection or invocation information.
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 low complexity, 100% schema coverage, and the explicit immutability constraints, the definition is nearly complete for selecting and invoking the tool. It would be fully complete if it addressed the effect of replacing options on existing data and clarified the update semantics, since there are no annotations or output schema.
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%, so the baseline is 3; the schema already documents id, name, options, and position. The description adds high-level meaning for name and options but adds no per-parameter detail beyond what the schema provides.
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 operation ('Rename a custom field or change its dropdown options') and names an explicit resource, which distinguishes it from custom_fields_create/delete/set_value. It loses the top score because it omits the position-update capability from the high-level purpose, even though the schema includes position.
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 clear context for when this tool is appropriate and names an alternative for the immutability limits ('create a new field if you need either' for entity_type/field_key). It does not explicitly contrast with custom_fields_set_value or describe when not to use the tool for type changes, so it falls short of fully explicit when/when-not guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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