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

With no annotations provided, the description carries the full behavioral burden and does well: it discloses the required subscription tier, the maximum span and look-back per accuracy, and the CSV emission shape (one row per point and currency with header). It does not mention rate limits, error behavior, or what happens when the span limits are exceeded, which keeps it short of a 5.

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 purpose and plan requirement are front-loaded before the bulleted accuracy table, and the bullets are scannable rather than prose. It is somewhat long, but nearly every clause carries a hard constraint an agent needs to construct a valid call.

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 7-parameter, no-output-schema tool there is no schema to fall back on for return values, and the description covers the CSV case in detail while leaving the default JSON structure implicit. Combined with the plan and span constraints, an agent has enough to call correctly, though the JSON response shape is not spelled out.

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 baseline is 3, and the description adds genuine meaning beyond it: the accuracy enum values are tied to concrete span/look-back constraints on datetime_start and datetime_end, and format=csv is explained in terms of row layout. Only the currencies/type/base_currency semantics remain purely schema-documented.

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 opening sentence gives a precise verb+resource+scope: returns exchange rates for every interval between datetime_start and datetime_end at a chosen accuracy. It is clearly a multi-point series tool, which implicitly separates it from a single-latest or single-conversion tool, but it never names or contrasts with siblings like getHistorical or getLatest, so an agent must infer the boundary.

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?

It states a real prerequisite ('Requires a plan that includes the range endpoint (medium and up)') and exhaustive per-accuracy span/look-back limits, which govern when a call will succeed. However, there is no guidance on when to choose getRange over getHistorical, getAverage, or getFluctuation — usage is implied by the name and parameter set rather than explained.

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