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

The readOnlyHint annotation already covers non-mutation, but the description adds valuable operational context: no charge is incurred, the minimum polling interval, the precise meaning of 'active', and the fact that credentials never enter chat. This goes well beyond what annotations alone provide.

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?

Three concise, front-loaded sentences with no wasted words. Each sentence earns its place: what the tool does, how often to poll, what counts as success, and what to do next.

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 zero-parameter read-only status check with an output schema, the description is complete. It covers when to call, the required cadence, the meaning of the result, privacy expectations, and the subsequent action. Nothing an agent needs to invoke it correctly is missing.

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?

The tool has zero parameters, so the baseline is 4. The description mentions the session header in prose, but since it is not a declared input parameter, no additional parameter documentation is needed.

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 the specific action 'Check' on a clearly defined resource ('privately connected signup-free session') and adds the key success criterion: 'Only active means credits/access are confirmed.' It also distinguishes itself from billing-related siblings by specifying 'after human payment' and 'No charge.'

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 guidance on when to use it: after human payment, to confirm credits/access, and polling no faster than five seconds apart. It also explains the follow-up action with the same session header. It does not explicitly name alternatives or exclusion conditions, so it stops short of a 5.

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