Custom Field Capabilities Add

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

Annotations already cover safety (readOnlyHint=false, destructiveHint=false), and the description adds genuinely useful operational context beyond them: the API is flagged as unstable, the required OAuth scope is named, and the HTTP verb/path is disclosed. It does not mention that idempotentHint=false means repeating the call may append a duplicate capability, which is the main behavioral risk here.

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 action in the first clause, followed by compact metadata lines (endpoint, scope, version). No filler; the only slight redundancy is repeating 'unstable' twice when once would suffice.

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 mutation tool with annotations covering safety, no output schema, and full schema coverage, the description supplies the remaining operational essentials: endpoint shape, auth scope, and API stability. The one substantive gap is that a 'capability' is never defined in either the description or 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 all four parameters (entity, namespace, slug, capability) are already documented in the schema, including the entity enum. The description only mirrors the path structure and adds nothing about the shape or semantics of the 'capability' payload, which the schema also punts on with 'per the API reference'.

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+resource: adding a capability to a custom field definition, with the exact HTTP endpoint showing the path parameters. It is distinguishable from the sibling capabilities_list/_remove and custom_field_defs_* tools by the verb, though it never names those siblings.

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?

Usage is implied by the endpoint and the required scope (read_products/write_products), but there is no explicit statement of when to call this versus custom_field_defs_create/update or when a capability should be attached rather than set at definition creation.

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