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

With no annotations, the description bears the full burden of behavioral disclosure. It reveals that the tool is FREE and returns a cost breakdown, which implies a read-only probe. However, it does not explicitly state that it does not execute the actual x402 request or what side effects might occur (e.g., hitting the target URL for pricing). The description adds some transparency but lacks explicit guarantees about safety and behavior beyond the free aspect.

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 extremely concise, consisting of one short sentence with a clarifying phrase. It front-loads the core purpose ('Get dynamic pricing') and appends essential behavioral details about cost breakdown and free status. Every word earns its place, with no unnecessary filler or repetition of schema 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?

For a tool with a single parameter and no output schema, the description is fairly informative (mentions cost components and free nature). However, it omits details about the return format (e.g., string, number, units) and does not clarify whether the tool actually contacts the target URL to probe pricing. It is adequate but could be more complete for an agent to fully anticipate outcomes.

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 input schema has 100% coverage: targetUrl is described as 'The x402-protected target URL to probe for pricing.' The tool description adds minimal extra meaning beyond that, merely contextualizing it as part of 'proxy requests' and 'target cost.' Since the schema already covers the parameter fully, the description provides no significant additional semantics, warranting the baseline score of 3.

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: 'Get dynamic pricing for x402 proxy requests.' It specifies the verb (Get), resource (dynamic pricing), and scope (x402 proxy requests), and distinguishes itself from siblings like x402_proxy or x402_send by focusing solely on pricing. The added detail about returning total cost (proxy fee + target cost) further clarifies its specific role.

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 implies usage when pricing information is needed ('Get dynamic pricing') and notes it's FREE, suggesting it can be used without cost. However, it does not explicitly state when to use this tool versus alternatives like x402_proxy or x402_send, nor does it provide exclusions or prerequisites. Usage context is present but not fully explicit.

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