Update Custom Field

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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=true, and openWorldHint=true, so the safety profile is covered. The description adds the genuinely useful deprecation context, but says nothing about which attributes are mutable, whether omitted attributes are preserved, or any auth/rate constraints.

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?

Two short sentences with the deprecation warning front-loaded ahead of the functional statement. Nothing is wasted and an agent scanning the list will see the critical migration signal first.

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?

An output schema exists and annotations cover the mutability profile, so the description needn't explain returns. However, for a nested-object mutation tool it should say which form-field endpoint replaces it and whether existing custom fields still need updating here; that routing detail is missing.

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 50%, and the top-level id property is thoroughly documented in the schema itself, including the note that there is no custom_field_id argument. The description only echoes 'by id' and adds no meaning about the nested data/attributes payload, so it neither compensates for the gap nor duplicates 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?

States a specific verb and resource ('Update a specific custom field by id') and leads with a deprecation flag, so an agent knows immediately what the tool does and that it is being retired. It does not differentiate from update_form_field beyond the deprecation pointer, but the core purpose is unambiguous.

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 names the preferred alternative ('Use form field endpoints instead'), which is a clear when-not-to-use signal, and it routes directly to siblings like update_form_field/create_form_field. It stops short of stating the one condition under which this tool is still the right call (e.g., legacy custom fields not yet migrated).

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