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

With no annotations, the description carries the full burden. It does add real behavioral value by explaining the interpretation rule for results ('lower is better' for selling, 'higher is better' for buying) and clarifying these are TT (telegraphic transfer) rates. It does not state that the operation is read-only, whether data is cached/live, rate limits, or what the comparison output looks like.

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 sentences, zero filler, and the core purpose is front-loaded before the parameter guidance. Every clause carries information an agent needs.

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?

Adequate for a two-parameter, zero-required comparison tool, and the side semantics are covered well. Missing is any indication of the return shape (e.g. a per-bank rate list) and any routing hint among the three sibling FX tools, which matters given there is no output schema to fall back on.

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 only 50% — the enum values for side are listed but never explained in the schema, and the description fills exactly that gap by defining what selling and buying mean and which direction is favorable. The currency parameter is already documented in the schema, so no compensation is needed there.

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 verb and resource ('Compare current Thai bank TT rates') with the scope narrowed to 'one currency', which is more precise than the tool name alone. It does not explicitly distinguish itself from siblings like get_best_thai_fx_rate, but the comparison-across-banks framing is reasonably self-evident.

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 gives genuine conditional guidance for the side parameter ('use side=selling when paying THB...'), which is useful. However, it offers no guidance on when to choose this tool over get_best_thai_fx_rate or get_thai_fx_history, so tool-level selection is left to inference.

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