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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, establishing this is a safe read-only operation. The description adds behavioral context: it explains the scoring logic (ranked by settled call counts, USDC totals, distinct buyers for x402; by inbound USDC.e transfers for MPP), the default windows (7d/30d, rolling), and the exclusion of the host's own wallet. This goes beyond what annotations provide, though it could mention rate limits or response pagination.

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 concise and front-loaded with the core purpose. Every sentence adds value: the first defines the tool, the second and third explain the two wire modes, the fourth gives the use case, and the last notes the host exclusion. 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?

Given the tool's moderate complexity (4 parameters, 3 enums, no required params, no nested objects, and a rich output schema not shown), the description is complete. It covers the two ledger modes, ranking criteria, default behaviors, and a non-obvious detail (host exclusion). The output schema is assumed to exist and handle return values, so the description need not explain them.

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 baseline is 3. The description adds value by explaining what each wire type's sort modes mean ('x402: rank by settled USDC (default) or by settled call count. mpp: usd = 7-day volume, calls = 7-day transfers (default).') which is not fully conveyed by the schema's enum descriptions. It also clarifies the default behavior for 'include' (external vs all). Slight deduction for not elaborating on how 'limit' affects results (e.g., rank ordering).

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 starts with a clear verb 'List ranked sellers from the on-chain settlement leaderboards' and immediately differentiates between wire=x402 and wire=mpp, specifying exactly what data is returned for each. This makes the tool's purpose distinct from siblings like 'catalog.search' (which searches for services) or 'demand.request' (which requests a service), as it focuses on ranking sellers by settled volumes.

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 states 'Use it to find other services in the open x402 / MPP ecosystem' and notes that 'This host's own wallet is excluded unless include is set to all', which guides when to use the tool vs alternatives. However, it does not explicitly mention when NOT to use it or compare to sibling tools like 'catalog.find' or 'catalog.search' for locating specific services.

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