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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered without the description. The description adds genuine value by enumerating the returned field attributes (name, type, label, required, choices), but says nothing about failure behavior for an invalid key or how the key/post-ID duality resolves.

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?

A single tight sentence that front-loads the action and resource before the parenthetical detail. Nothing is padded or redundant.

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 read-only lookup with full annotation coverage and no output schema, the description adequately conveys what is retrieved and the shape of the returned field definitions. Minor gaps remain around invalid-key handling, but the essential information an agent needs to call it is present.

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 both the 'key' format (group_abc123 or post ID) and the optional 'site_id' are already documented in the schema. The description adds no meaning beyond that, making the baseline 3 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 and resource ('Get a specific ACF field group') and clarifies the payload ('all its field definitions'). The word 'specific' hints at single-item retrieval, but it does not name or contrast with the sibling acf_list_field_groups, so differentiation is left to inference.

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 only implied: the requirement of a 'key'-based lookup suggests retrieving one known group, and the sibling list tool is never mentioned. No explicit when-to-use or when-not-to-use guidance is given.

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