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

With no annotations, the description carries full behavioral disclosure. It clearly reveals the x402 payment requirement, the 402 retry flow, that no account/commitment is needed, and the ranking behavior. It does not explicitly state read-only semantics or response shape, but for a scan tool the behavior is well disclosed.

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 core action is front-loaded in the first sentenceation. Payment and retry instructions are clearly separatedq The 'BEST COLD START' section adds scannable usage context without excessive length, though the capitalization is a bit promotional.

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 simple tool with only one optional limit parameter, the description covers the core function, ranking behavior, monetization flow, and fallback to sibling tools. It lacks an explicit note about return value structure (e.g., whether it returns names, prices, scores), but the absence of an output schema and the simple interface keep the hit minor.

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?

There is only one optional parameter and the schema already documents it as 'How many to return.' The description adds that the tool works without selecting a symbol and ranks the whole universe, which gives context but does not add much beyond the schema. Baseline 3 is appropriate because the parameter is fully documented in the schema.

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?

States a specific action ('Scan the FX snapshot and return currency pairs at a top (sell)'), a clear resource, and an explicit ordering ('ranked most-top first'). It is clearly distinguishable from the sibling scan_bottoms because it explicitly says 'top' versus bottoms, and contrasts with pitch by naming pairs instead of just counting them.

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 says this is the 'BEST COLD START' because no symbol needs to be selected and it ranks the whole universe. It also tells the agent that pitch gives the count while this tool gives the names, which provides clear when-to-use guidance. It does not explicitly say when NOT to use it versus scan_bottoms, but the sibling distinction is implied.

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