list_roles

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

With no annotations, the description carries the full burden and does well: it discloses that 'source' is 'channel-registry' (authoritative) in hosted mode vs 'observed-in-messages' in stdio mode, and warns that the inferred variant can under-report a member who never spoke. Permission or rate-limit context is absent, but the accuracy caveat is unusually valuable.

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?

Front-loaded with the core answer, then usage, then the source semantics. The historical aside about guessing names and reading rejection messages is narrative filler that does not help invocation, but it is a single clause and the rest is tight.

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?

An output schema exists, so return values need not be re-explained, yet the description still adds the mode-dependent meaning of 'source' and its reliability caveat. For a zero-param read tool this is complete.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate — the baseline for a parameterless tool is 4. The description correctly adds no parameter noise.

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 the resource and scope concretely: 'Who is in this channel', with the exact return shape ({roles, you, source}). It is clearly distinct from mutation siblings like add_role, though it does not explicitly name an alternative to distinguish it from channel_status.

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?

Gives two concrete reasons to call it ('to address anyone' and 'to know how many agree votes a protected pin will require'), which is real when-to-use guidance. It does not, however, state when not to use it or point to an alternative tool.

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