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

Goes beyond annotations by disclosing payment requirements ($0.05/call via x402, 402 response on non-payment) and the response structure (array of charge objects). Annotations already declare readOnly/idempotent, and the description adds valuable operational details without contradiction.

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 compact and well-structured with clear sections: purpose, usage, payment, and returns. Every sentence adds value, with no redundancy or filler.

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?

Despite having no output schema, the description fully explains the return format (array of charge objects with fields). It covers purpose, usage, payment, and output, making it complete for the tool's complexity and context.

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 does not add extra parameter-level semantics beyond what the schema already provides; it merely restates the tool's purpose. No additional meaning is given to line, country, port_code, or x_payment beyond schema descriptions.

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 explicitly states the tool's function: 'Get local charges at a port for a specific carrier' and enumerates the charge types (THC, BL/DO, seal fees). It clearly distinguishes the tool from siblings by focusing on port-local charges rather than broader rate calculations.

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?

Provides explicit usage context: 'Use this when calculating total shipping costs at origin or destination.' It names specific alternatives and complementary tools (shippingrates_dd_calculate, shippingrates_total_cost), giving clear guidance on when to use this tool versus others.

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