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

Annotations already declare readOnlyHint=false, destructiveHint=true, and idempotentHint=true, so the safety profile is covered. The description adds the mutation scope ('change its label or choice options') and a return note, but discloses nothing beyond annotations about auth needs or what the destructive replacement actually affects.

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?

Front-loaded with the core action, then a compact when-to-use line and a short example. Every sentence earns its place; only the explicit return note is mildly redundant given the output schema.

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?

For a low-complexity 4-parameter mutation tool, the description covers purpose, usage, and an example, while annotations handle safety and the output schema handles the return value. Auth/permission requirements are the only notable omission.

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 all four parameters are already documented, including the key-vs-label distinction and the option-replacement semantics. The description's 'by object_type + key' only restates schema content, so the baseline 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?

States a specific verb (patch) and resource (custom field) plus the exact editable fields (label, choice options), identified by object_type + key. It's clear enough to distinguish from create-style siblings like define_field, though it never names them explicitly.

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 explicit 'When to use' line gives a clear triggering context (admin renaming a field or changing its options) and an example. It lacks when-not guidance and does not route the agent to alternatives such as define_field or archive_field.

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