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

The readOnlyHint annotation already declares the safety profile, so the bar is lower. The description usefully adds that member contacts are returned alongside the group (not just the group record) and cites the REST endpoint, but it says nothing about pagination, error behavior, or authentication beyond what the annotation implies.

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 tightly packed sentences, front-loaded with the behavioral fact (member contacts included) before the endpoint reference. No filler or redundancy.

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 one-parameter read with no output schema, the description is nearly complete: it tells the agent what is returned (group plus members). It could go slightly further on the response shape or on what happens for an invalid id, but nothing critical to correct invocation is missing.

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 the single required contact_group_id is fully documented in the schema. The description's '<id>' placeholder mirrors the same information without adding format constraints or bounds. 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 and resource ('Fetch a contact group') and clarifies scope with 'and its member contacts', which distinguishes it from the sibling happyfox_list_contact_groups (plural listing). It stops short of naming that sibling explicitly, but the singular framing makes the retrieval-one-vs-list-many distinction inferable.

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 rather than stated: fetching by id is the obvious trigger. There is no explicit when-to-use guidance and no mention of alternatives such as happyfox_list_contact_groups or happyfox_get_contact, so the agent must infer the routing itself.

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