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

Beyond the readOnlyHint annotation, the description discloses meaningful permission behavior for private channels and older connections, plus the need to reconnect to grant user scopes. It does not cover pagination or return shape, but it adds substantial behavioral context that annotations alone do not provide.

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 purpose is front-loaded in the first sentence, followed by useful permission context. The final sentence repeats the schema's `account` guidance, which is mildly redundant but not disruptive.

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 read-only list tool with a fully documented schema and no output schema, the description covers the key uncertainty: private-channel visibility and workspace selection. It could add a bit more about returned identifiers or pagination behavior, but the core invocation context is present.

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 all three parameters are already documented in the schema. The description only repeats the `account` condition and otherwise adds no syntax or meaning beyond what the schema provides, making the baseline 3 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?

The description states a specific verb and resource: 'List one Slack channel's member user ids.' This distinguishes it from sibling tools like list_contacts and list_chatwork_room_members by naming the Slack channel scope and the returned member identifiers.

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?

It gives clear operational context: user-token scopes can read private channels even when the bot is absent, older connections are limited to bot-visible channels, and `account` is needed for multi-workspace setups. It does not explicitly compare against alternatives such as search_channels or read_channel, so it is not a full 5.

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