Read a Slack thread

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered; the description then adds real behavioral detail the annotations don't: results are ordered oldest first and the parent message is included in the result set. It stays silent on pagination behavior (limit default 50, max 200) and on whether you must page through large threads, which is the remaining gap.

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?

Two sentences, zero waste, with the ordering-and-parent guarantee front-loaded before the parameter note. Nothing is repeated from the schema or annotations.

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 4-parameter read tool with full schema coverage and covered safety annotations, this is close to complete: result ordering and parent inclusion are stated. The remaining omission is pagination guidance — with limit capped at 200 and a cursor parameter, an agent would benefit from knowing when to expect truncation.

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 the baseline is 3, but the description adds meaning the schema does not: thread_ts accepts the ts of the parent message *or of any message in the thread*, which actually extends the schema's narrower 'parent message' wording. That resolves a real ambiguity in how to call it.

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 ('Read') and resource ('replies in a thread') plus the ordering and the inclusion of the parent message, which is genuinely distinguishing information. It does not, however, contrast itself with the sibling check_replies or conversations_history, so an agent must infer which of the three thread-reading tools applies.

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?

Usage is implied by the resource name — you call it when you want a thread's contents — but there is no explicit 'use this instead of X when Y' guidance despite check_replies and conversations_history being obvious overlaps. The thread_ts clarification hints at the calling context but doesn't set boundaries.

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