List channel messages

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds useful behavioral context: it returns compact summaries with specific fields (id, from, created, body, webUrl) and orders results most recent first. It doesn't mention pagination or the top parameter's cap, but the schema covers top's maximum. A 4 is appropriate because the description adds meaningful behavioral detail beyond annotations.

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, front-loaded with the core action and ordering, then the return format, then the sibling routing. No wasted words.

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 full schema coverage and annotations covering safety, the description is nearly complete. It could mention pagination or the TEAMS_MAX_RESULTS cap behavior, but the schema already documents top's maximum and the description gives the return shape. Minor gap, so 4 rather than 5.

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 the schema already documents all three parameters. The description adds the 'most recent first' ordering and the compact summary fields, which indirectly clarifies what top controls, but it doesn't add new parameter-level meaning beyond the schema. Baseline 3 is correct.

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 clearly states the tool lists top-level messages in a channel, most recent first, and distinguishes it from list_message_replies for thread replies. It names the specific resource (channel messages) and the verb (list), making it easy for an agent to select correctly among siblings.

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 to use list_message_replies for a message's thread, providing a clear alternative and when-not-to-use condition. It also implies this is for top-level messages only, which is a clear usage boundary.

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