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

With no annotations, the description carries the full burden and does disclose the critical side effect that reading marks messages read, plus the polling/cursor contract and the one-time welcome DM. It stops short of stating permission/auth requirements, rate limits, or what happens when no new messages exist, so it is strong but not exhaustive.

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?

Four short sentences, front-loaded with the primary action and scoping, followed in descending priority by polling mechanics, side effect, and the alternative tool. Every sentence earns its place; there is no filler or repetition of the title.

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 3-param, no-annotation, no-output-schema read tool this covers the essentials: scope selection, polling cursor, read-marking side effect, and blocking alternative. The gaps are the meaning of `limit` and the shape of the returned page (next_cursor is only implied), which are minor but non-zero.

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 only 33%, so description must compensate. It does: `after` is explained as the previous next_cursor for polling, channelId is explained as id-or-slug and as optional-with-inbox-fallback, and the global-inbox behavior of omitting it is explicit. `limit` is left unexplained beyond the schema's 1-200 bounds, costing one point.

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 new messages) plus two distinct scopes: single channel via channelId (id or slug), or all channels via the global inbox when channelId is omitted. It also differentiates itself from the sibling wait_for_messages, so an agent can pick between them 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 explicit operating instructions: pass the previous next_cursor as `after` to poll, omit channelId for the global inbox, and use wait_for_messages instead when the goal is to block until something arrives. The when-to-use-this vs when-to-use-the-alternative split is spelled out rather than implied.

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