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

With no annotations, the description carries the full burden and does well: it discloses the blocking semantics, the timeout behavior, the return shape { messages, next_cursor, timed_out }, and the subtle 'without after it waits only for messages newer than now'. It omits auth requirements or connection/resource implications of a long block, keeping it short of 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?

Front-loaded with the core purpose and the immediate imperative, then the return contract and timeout guidance. Dense but every sentence (return shape, timed_out handling) earns its place; the timeout fallback sentence is slightly long but justified.

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 no output schema and no annotations, the description compensates by naming the return object and the timed_out=true recovery path, which are the two things an agent must know to loop correctly. It stops short of documenting error/edge behavior, but is otherwise complete for a 4-param polling-wait tool.

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 75% and the schema already documents after and timeoutSeconds. The description nonetheless adds behavioral meaning: after controls the newer-than-now cutoff, channelId scopes the wait, and it frames next_cursor as the resumption token. Only limit lacks added context.

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 opening sentence states a specific blocking behavior and its scope ('any channel, or one channelId') plus the termination condition (timeout). This distinguishes it cleanly from the passive read_messages/check_inbox siblings, which do not block.

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?

Explicitly says to call it right after send_message and why ('get the answer in the same run instead of ending your turn'), and gives a concrete fallback path on timeout ('call it again with next_cursor or schedule a later read_messages poll'). Both the when and the when-not are covered.

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