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

Annotations already declare non-readonly, non-destructive, non-idempotent behavior, so the description does not need to repeat side-effect semantics. It adds valuable context beyond annotations: per-call pricing, the USDC/Solana payment requirement, the x402 challenge-retry mechanism, and the HTTP equivalent endpoint.

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?

The description is two sentences with the core purpose and limit front-loaded. The payment details are dense but operationally necessary for a paid x402 tool, and the HTTP equivalent is a compact addition.

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 one-parameter tool with full schema coverage and no output schema, the description covers the critical calling context: batch limit, cost, payment flow, and alternate HTTP endpoint. It does not describe the return shape or error behavior, which is a minor gap for a calculation endpoint.

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 the single items parameter and its nested item shape are already documented. The description repeats the batch maximum of 100 but does not add factor_id, quantity, or year semantics beyond what the schema provides.

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 states a specific verb and resource: 'Calculate CO2e'. It also adds the batch scope: 'up to 100 activities in one call', which distinguishes it from the single-item sibling emissions_calculate.

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?

It gives clear batch-size guidance and a detailed payment/retry flow for x402, which is useful operational context. However, it does not explicitly say when to use this tool rather than emissions_calculate or name exclusions, so usage is mostly implied by the 'batch' scope and payment instructions.

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