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

Annotations already declare read-only, idempotent, non-destructive, open-world behavior, so the description could have coasted. Instead it discloses the 30-second cap, that the call returns the current snapshot rather than erroring at timeout, and that it does not block other actions in the session — genuine behavioral context beyond the structured fields.

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 behavior and the timeout contract, then the safety caveat. Every sentence carries distinct information: wait semantics, time bound, concurrency guarantee, and injection warning.

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 three-parameter tool with no output schema and low schema coverage, the biggest gap is the return value: the agent is told it gets 'a snapshot' but not what fields it holds or how to use its revision for the next call. The safety guidance is thorough, but the operational picture is incomplete.

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% — session is documented, while timeoutMs and afterRevision carry no schema description. The description partially compensates by explaining afterRevision's semantics and the 30-second ceiling, but it never mentions the timeoutMs parameter by name or explains how to choose a smaller value.

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 — wait for a snapshot newer than afterRevision, else return the current one — so the long-poll nature is clear. It never says what a 'snapshot' actually contains (room state, revision counter?), which leaves the resource slightly abstract, but the operation itself is unambiguous.

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 rather than stated: the afterRevision parameter signals 'call this after you already have a revision and want the next one.' It adds a useful non-blocking guarantee, but never names alternatives such as session_observe or chat_history_export, nor says when to prefer a plain read over waiting.

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