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

With no annotations present, the description carries the full behavioral burden and does so well: it discloses the returned fields (rate used, publication date, euro-crossed flag), daily publication cadence, reproducibility, 90-day date limit, and cost/payment method. This is substantially more than the schema or annotations provide.

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 front-loaded with the usage trigger, then efficiently covers scope, return values, distinction from live quotes, and cost. Every sentence adds useful information and there is no 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?

There is no output schema and no annotations, yet the description explains the return fields, publication timing, date limits, currency coverage, and payment model. For a simple four-parameter conversion tool, an agent has everything needed to call it 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 schema already documents all four parameters, including defaults for amount and date. The description reinforces the currency universe and date window but does not add syntax or formatting details beyond what the schema provides, so the baseline 3 is appropriate.

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 states a specific verb and resource: convert money between currencies using the European Central Bank's official reference rates, with a clear ~30-currency and 90-day scope. It also explicitly distinguishes itself from a live market quote, so an agent can tell what this tool is and is not.

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 opening 'Use when an agent has to convert money in a figure someone will audit' gives a clear triggering condition, and 'not a live market quote' supplies an exclusion. It does not name an alternative tool for non-auditable or live conversions, but the context is otherwise strong.

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