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

With annotations declaring readOnlyHint=true, the description adds genuinely non-obvious context: the call has the side effect of keeping the session alive, which is not conveyed by any structured field. Returned content ('time left, usage, limits') is also sketched, though format and units are absent.

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 fragments, zero waste, but the telegraphic style omits the verb and connective logic that would make the sentence parseable on first read. It is brief without being well-structured.

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 two-required-parameter read tool with a fully described schema and safety annotations, the description covers the essential unknowns: what comes back and the keep-alive side effect. Only error/expiry behavior is missing, which is minor given no output schema and a simple input surface.

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 100%, so both session_id and secret are already documented in the schema. The description adds nothing about the parameters (e.g., what happens with an expired secret), so 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?

The description names the payload ('Time left, usage, limits') but never gives a verb, so it's unclear whether it retrieves status, refreshes it, or both. It also does not distinguish itself from siblings like extend_session or close_session, which an agent could easily confuse with a session-keeping-alive call.

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?

There is no explicit guidance on when to call this versus extend_session (which presumably also affects session lifetime) or close_session. The phrase 'keeps the session alive' hints at a heartbeat usage, but the agent must infer it rather than being told.

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