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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true, so the safety profile is covered. The description adds genuine context the annotations don't: smart groups are excluded, and the returned fields include membership status (Added/Removed/Pending). It stops short of disclosing default behavior when neither identifier is supplied or what pagination looks like.

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 tight sentences front-load the core behavior and the smart-group exclusion, followed by the APIv4 entity reference for traceability. Nothing is redundant, though the parenthetical could be split to make the two modes easier to parse.

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?

With zero required parameters and no output schema, the definition should state what happens when neither group_id nor contact_id is provided (list everything? error?). It covers return fields informally but leaves this default-behavior gap for a tool an agent can call with no arguments.

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 carries a description including defaults and the next_offset pattern, so the schema does the heavy lifting and a baseline 3 applies. The description adds only the conceptual framing of group_id vs contact_id as opposite directions, which the schema descriptions already convey.

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?

The description names the two access modes precisely: members of one static group, or groups of one contact, plus what fields come back (contact, group, membership status). It differentiates itself from civicrm_list_groups by pointing at the underlying GroupContact.get entity, though it never names sibling tools as alternatives.

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 dual-mode phrasing and there is a partial exclusion ('Smart groups are computed by CiviCRM and not listed here'), which is a real when-not. But it gives no explicit guidance on when to prefer this over civicrm_list_groups or civicrm_list_memberships, and the schema fields are what actually route the caller (group_id 'from civicrm_list_groups').

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