update_usergroup_members

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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the description does not need to repeat that this is a mutating operation. It adds value by specifying the exact destructive nature ('replacing the current membership entirely') and the constraint that user_ids must contain at least one user. This goes beyond the annotation and gives the agent important behavioral context. It does not, however, mention any potential failure modes (e.g., invalid usergroup or user IDs), but that is not required given the annotation coverage.

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 well-structured with an Args section and a Returns section. It is concise—only three sentences of core content—and every sentence provides necessary information: the action, parameter explanations, and return value. It is front-loaded with the primary behavior, then details, and ends with the return type. Nothing is redundant or extraneous.

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 two-parameter tool with a simple output (True/False), the description is entirely sufficient. It specifies the return type, explains both parameters, gives constraints, and points to the alternative for a different scenario. There is no missing information that an agent needs to correctly invoke the tool, especially given that annotations already supply the safety profile (destructive, not read-only).

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 0%, so the description must carry the full burden of explaining parameters. It does so effectively: usergroup_id is described as 'The usergroup ID (S...)' and user_ids as 'List of user IDs (U...)' with the critical constraint 'Must contain at least one user.' This adds format hints and constraints that the schema (which only provides types) does not convey, fully compensating for the lack of schema-level descriptions.

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 states a clear, specific action: 'Set the members of a Slack usergroup, replacing the current membership entirely.' It names the verb ('set'), the resource ('members of a Slack usergroup'), and the key behavior ('replacing entirely'). It also distinguishes from the sibling clear_usergroup by mentioning the alternative for removing all members, so an agent can immediately tell which tool to use.

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 explicitly says when to use this tool (to set/replace membership) and when NOT to use it: 'Must contain at least one user — use clear_usergroup to remove all members.' This gives a clear exclusion and points to the correct sibling for that case. No ambiguity remains about when to select this tool over alternatives.

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