x402_forecast

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

With no annotations, the description takes on the full burden. It clearly discloses read-only behavior ('Read-only — nothing is paid or mutated'), the requirement for an agent key, and the return structure (aggregated USDC cost projection and policyPreflight block). What is missing is potential error behavior or rate limits, but the key behavioral aspects are covered.

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 three sentences, front-loaded with the core purpose, followed by return details and usage guidance. Every sentence adds value with no repetition or extraneous information.

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?

The description explains expected outputs (aggregated cost and policyPreflight) since no output schema exists. It covers constraints (50 items, repeat count), safety (read-only), and prerequisites (agent key). For a moderately complex tool with a nested array parameter, this is fully sufficient.

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 description coverage is 100%, so the baseline is 3. The description adds context by explaining the 'plan' concept and the repeat count, but these are already present in the schema (maxItems: 50, count property). It does not introduce new parameter semantics beyond what the schema already documents.

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 function: 'Batch cost forecast + policy preflight for a PLAN of paid calls'. It uses a specific verb and resource, and distinguishes from siblings like estimate_x402_cost by emphasizing batch processing and policy preflight. The scope is well-defined with the 50-call limit.

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?

Explicitly states when to use: 'Use to validate a multi-step plan in one round-trip instead of estimating call-by-call.' This provides a clear alternative and context. It also mentions the prerequisite of an agent key and emphasizes read-only nature, guiding safe usage.

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