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

The annotations already declare readOnlyHint=true, idempotentHint=true, and openWorldHint=false, so the safety profile is covered. The description still adds useful context beyond them: the exact content of the response and that it is returned in Moda's published wording verbatim, which matters for downstream quoting. It does not mention error behavior when a group is unknown, which is a minor gap given the annotations.

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?

The description is front-loaded with the return content and the parameter guidance follows immediately, with no filler sentences. The first sentence is long and list-dense, but each listed item is informative rather than redundant, and the closing note on response format is brief.

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 a single optional parameter, no nested objects, and no output schema, this description carries the burden of explaining the return value, and it does so by naming the fields the response covers and the wording convention. It is slightly vague about the actual JSON structure, but nothing needed to invoke the tool correctly 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 coverage is 100% and the single parameter is already documented, so the baseline would be 3. The description goes beyond that by giving concrete accepted forms ('Moda Watch Club 10K & Under or modahype') and by explaining what the omitted-parameter result contains, which the schema does not state.

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 uses a specific verb ('Returns') with a specific resource ('the posting rules for a Moda Facebook group') and enumerates the rule categories it covers: purpose, price range, hashtag, declined words, joining, and global rules. That enumeration makes it distinguishable from siblings like find_moda_groups or search_moda_guides without needing a schema lookup.

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 semantics of omitting the parameter are stated explicitly: 'Leave it out for the rules every group shares and the list of groups,' which tells the agent when to call with and without the argument. However, no sibling alternative is named, so the agent is not told, for example, to use find_moda_groups to discover a group name before calling this.

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