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

readOnlyHint=true already tells the agent this is a safe read. The description adds useful behavioral context the annotation doesn't: the results are pending (not sent) messages and the returned id feeds a cancellation workflow. It stops short of describing pagination behavior or result shape, 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?

Two tight sentences, front-loaded with the verb and resource, then the filter rule and the cross-tool handoff. Zero filler.

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?

No output schema exists, but the description points at the salient return field (`id`) and its downstream use, which is enough for a read-only list tool whose annotations carry the safety profile. Minor gap: nothing about pagination beyond the schema's cursor, though the schema covers it.

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 limit, cursor, account and channel are all documented in the schema. The description restates the channel filtering semantics (channel vs. omit for all), which is already fully covered by the schema and adds no new syntax or format detail. Baseline 3 applies.

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 (List) and resource (a Slack workspace's pending scheduled messages) with the underlying API method named, and explicitly routes to the sibling cancel_scheduled_message. An agent can distinguish it from schedule_message and other list tools without opening a 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 clear context on filtering — supply `channel` or omit it for all channels — and describes the follow-on action (use the returned `id` with cancel_scheduled_message). No explicit when-not or exclusion guidance, but the operational context is unambiguous.

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