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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), but the description adds genuinely new behavior: the tool is always free, never consumes a free-trial call, and does not require agent_id or tx_hash. It stops short of disclosing result limits, pagination, or ranking mechanics, so not a full 5.

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?

Front-loaded with the core purpose, then cleanly segmented into WHEN TO USE / WHEN NOT TO USE / PARAMETER INTERACTIONS. The trailing example is mildly redundant with the schema's own example and repeats the tool name verbatim, which costs a small amount of space.

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?

An output schema exists, so return-value detail is not required, yet the description still summarizes what comes back (pricing, trust scores, SLA tiers). Combined with the discovery-vs-execution routing and the free/no-trial-consumption note, an agent has everything needed to call this correctly.

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 goes further by stating a parameter interaction rule — supply keywords/domain in query and omit agent_id and tx_hash for discovery — which is a conditional usage rule not derivable from the individual field 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?

Specific verb (Search), specific resource (490+ indexed MCP and x402 tools), and a concrete outcome (ranked endpoints with pricing, trust scores, SLA tiers). It is clearly distinguishable from execute_marketplace_tool and execute_workflow_bundle without opening any schema.

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?

Explicit WHEN TO USE ('call first to discover which native slug or external endpoint matches your task') and WHEN NOT TO USE ('do not use to execute a tool directly') sections, each naming the correct alternative. This is exactly the routing guidance an agent needs.

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