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

No annotations are provided, so the description carries the full burden. It does add meaningful behavioral context beyond the schema by disclosing the data source (European Central Bank reference rates), which implies provenance and periodic refresh. However, it does not disclose what happens with unknown currency codes, whether all rates are returned when symbols is omitted, or the response structure, which are gaps for a tool with zero annotation coverage.

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 with no filler: the verb, resource, default, and optional filtering are front-loaded, and the source attribution earns its place because it communicates data provenance. Nothing could be removed without losing information.

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 low-complexity tool with two optional parameters fully documented in the schema and no annotations, the description covers all invocation essentials: what is fetched, the base default, optional filtering, and data source. The only notable gap is the unstated return shape, since no output schema exists, but the tool is simple enough that an agent can proceed without it.

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 even with no parameter info in the description. The description merely reinforces what the schema already states (default USD base, optional comma-separated targets); it adds no new semantic detail such as accepted value formats beyond the schema's own examples.

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 names a specific verb ('Get'), a clear resource ('latest foreign-exchange rates'), and a scope ('for a base currency, optionally limited to specific target currencies'). The word 'latest' distinguishes it from the sibling tools fx_historical and fx_timeseries, while 'rates' separates it from fx_convert and fx_currencies, so an agent can pick it without opening schemas.

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 provides clear context — this is the current-rates tool with an ECB source and optional symbol filtering — so usage is implied. However, it never explicitly names alternatives or states when NOT to use it (e.g., 'for past dates use fx_historical'), leaving the agent to infer the boundary against siblings.

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