Add contact to group

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

The description discloses idempotency ('updates an existing row rather than creating duplicates') and a write permission requirement. Since no annotations are provided, this is good but could mention error handling or additional side effects.

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 concise sentences, front-loaded with the action and key behavioral trait (idempotency). No unnecessary words, every sentence adds value.

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 simple 2-parameter tool with no output schema, the description covers action, idempotency, and a requirement. It could be slightly improved by noting error conditions or expected behavior when contact already in group, but meets minimum completeness.

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 50% (only group_id has a description). The tool description does not add any parameter meaning beyond what the schema provides, failing to compensate for the missing contact_id description.

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 clearly states the verb 'Add' and resource 'contact to a group', specifying the exact status 'Added' and idempotent behavior, which distinguishes it from siblings like civicrm_remove_from_group.

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 description provides a critical prerequisite: 'Requires CIVICRM_ALLOW_WRITES=true', which helps the agent decide readiness. It lacks explicit 'when to use' or 'when not to use' compared to alternatives, but the sibling set includes a removal tool, so purpose differentiation is implied.

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