topup_x402_session

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

No annotations are provided, so the description must carry the full burden. It discloses the requirement of a payment signature for traffic additions and that duration-only extensions are free, which is critical behavioral information. However, it lacks details on return behavior, error conditions, idempotency, or what happens if the session is expired.

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 sentences, no fluff. The first sentence states the purpose concisely, and the second adds essential condition information. Every sentence earns its place.

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?

Given the tool's moderate complexity (4 parameters, no output schema), the description covers core functionality and a key condition. It does not explain return values or operational prerequisites (e.g., session must exist), but it is largely sufficient for a focused mutation 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 100%, so baseline is 3. The description adds value beyond the schema by explaining that 'paymentSignature' is required only for traffic top-ups (though the schema marks it required unconditionally), and clarifies that 'addTrafficGB' and 'addDurationSeconds' are optional. This nuance aids the agent in understanding parameter relationships.

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 clearly states the tool's purpose: 'Top up a session with additional traffic and/or duration.' It uses a specific verb ('top up') and resource ('session'), distinguishing it from sibling tools like 'get_x402_session' (retrieval) and 'calculate_x402_topup' (calculation).

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?

The description provides clear guidance on when to use this tool: it notes that payment signature is required for traffic top-ups and that duration-only extensions are free. This helps the agent understand the payment condition, though it does not explicitly contrast with alternatives or specify when not to use it.

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