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

With no annotations, the description carries the behavioral burden. It clearly defines what 'best' means for each side ('lowest sell price' vs 'highest buy price') and signals real-time data with 'right now.' It does not describe the return shape or edge cases, but the central behavioral ambiguity is resolved.

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?

Two concise sentences with no filler. The core result is front-loaded, and the side nuance is packed into the second sentence efficiently. Every clause 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?

For a 2-parameter query with full schema coverage, the description is mostly complete: it defines the result, the side semantics, and the schema covers currency format. It could benefit from a brief note on return format or when to prefer sibling tools like list_houses or get_rates, so it is not fully self-contained.

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 coverage is 100%, so the baseline is 3. The description adds meaningful nuance to the 'side' parameter by explaining the price direction ('buy' = lowest sell price, 'sell' = highest buy price), which goes beyond the schema's generic phrasing. Currency is adequately documented in the schema as an ISO code.

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 the tool returns 'the single best casa de cambio right now to buy or sell a currency,' a specific outcome that distinguishes it from siblings like list_houses (all houses) and get_rates (rates). The side semantics are defined up front, leaving no ambiguity about what the tool does.

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 intended use is implied: call this when you need the current best exchange house for a given currency and side. However, it does not explicitly name alternatives or exclusions, such as using list_houses to see all exchange houses or get_rates for historical rates, so an agent must infer when this tool is preferred.

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