Read Slack channel history

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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered; the description adds real behavioral context – result ordering (newest first), pagination direction, and the fact that thread replies are omitted. It stops short of mentioning rate limits or any auth scope quirks, so not a 5.

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?

Three short sentences, front-loaded with what it returns and the ordering, then paging, then the exclusion. Every clause carries information an agent would otherwise have to guess.

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 annotations covering the read-only/open-world profile and the schema covering all six parameters, this description covers what remains: result scope, ordering, pagination mechanics, and thread exclusion. No output schema exists, so no return-shape explanation is owed.

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%, so every parameter including limit, latest, oldest, and include_activity is already documented. The description only reinforces `channel` (repeating the schema's own wording) and adds a bit on `cursor`; it does not explain the relative/ISO time formats that make oldest/latest non-obvious.

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 ('Read recent messages from a channel or DM'), plus ordering ('newest first') and the DM/channel scope. It explicitly sets itself apart from conversations_replies, so an agent can distinguish it without opening either schema.

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 both the paging procedure ('use `cursor` from the previous response to page further back') and the exclusion rule with a named alternative ('Thread replies are not included; use conversations_replies for those'). The condition that selects the sibling is explicit, not inferred.

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