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

Annotations already declare destructiveHint=true, idempotentHint=true, and openWorldHint=false, but the description adds the non-obvious tier gate and authorization model, plus an out-of-band constraint (scope changes require /promote). It stops short of noting that replacing the options list can invalidate existing stored values.

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 compact sentences, front-loaded with the action and its sub-operations, followed by prerequisites and the scope exception. No filler or restated title text.

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?

No output schema exists, but this mutation tool's description covers permissions, entitlements, and the scope-change escape hatch, which is what an agent most needs before calling it. Minor gap: it doesn't say what happens to existing values when the options list is replaced.

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 coverage is 100% and every parameter already carries its own description, so the schema does the heavy lifting. The description's enumerated operations loosely map to name/options/required/defaultValue but add no format or constraint detail beyond the schema (e.g., it doesn't explain defId usage).

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?

Specific verb (update) plus resource (custom field definition), with the mutable aspects enumerated: rename, options, required, default. This cleanly separates it from create_custom_field_def, list_custom_field_defs, and set_custom_field_value (which sets values, not definitions).

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?

States the entitlement and role prerequisites (customFields PRO+, org admin/manager, or project owner/manager for project-scoped fields) and explicitly routes scope changes to the REST /promote endpoint instead. It does not explicitly contrast with the sibling value-setting tools, so not a full 5.

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