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

With no annotations, the description carries the full burden. It discloses the paid nature, the x_payment workflow, and the inclusion of the OP-stack L1 data fee. It does not mention rate limits or return format, but the core behavioral traits are well covered. No contradiction with annotations (none provided).

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 sentences with no wasted words. The first sentence front-loads the core purpose, the second explains the payment flow, and the third offers the alternative. 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 moderate complexity (4 optional params, no output schema, no annotations), the description covers the essential context: the ranking output is implied, the paid flow is explained, and the differentiator from pricing is stated. It could mention return shape or pagination, but it is largely complete for an agent to use effectively.

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 schema already provides 100% coverage with descriptions for each parameter, including the x_payment two-step semantics. The tool description adds little beyond reinforcing the payment flow and noting the L1 fee inclusion, which is contextual rather than parameter-specific. Baseline of 3 is appropriate.

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: 'Rank every supported chain by all-in USD transaction cost' with a specific verb and resource. It also frames the use case ('where should I send this' routing decision) and distinguishes itself from the pricing tool, making it unambiguous.

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 explicitly explains when to use this tool versus the 'pricing' alternative ('The free pricing tool lists every price at once'), and details the paid two-step invocation flow (call without x_payment, sign terms, call again). This gives clear context and exclusions.

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