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

With no annotations, the description carries the behavioral burden and does so well: it discloses the weekend/holiday fallback to the most recent working day, the presence of a `note` explaining the substitution, and the returned fields. It does not cover error behavior (unsupported currency codes, non-positive amounts), leaving a minor gap.

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?

Three short sentences, front-loaded with the core action and scope, then the return values, then the non-obvious date behavior. Every sentence carries distinct information with no padding.

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?

An output schema exists so return values need not be detailed, yet the description still helpfully names rate_date and note. Combined with the fallback rule, it is nearly complete; only error/validation behavior for invalid currencies or amounts is unaddressed.

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 baseline is 3, and the description adds genuine meaning on top by explaining how `date` behaves on non-working days and that omitted dates yield the latest rate. It adds little beyond the schema for amount/from_currency/to_currency, but the date semantics are a real contribution.

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 (Convert), resource (an amount from one currency to another), and scope (at the ECB reference rate). This cleanly separates it from sibling tools like latest_rates, historical_rate and rate_timeseries, which surface rates rather than performing a conversion.

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 clear operational context: omit `date` for the latest rate, and supply a date for a specific rate. It does not explicitly name or exclude the sibling tools (e.g. when to prefer historical_rate instead), so it stops short of full when/when-not guidance.

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

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

With no annotations, the description carries the full burden and does substantial work: it discloses the working-day publication rule, that weekends/holidays return the most recent working day rather than an error, the presence of a `note` field explaining substitutions, and the per-currency feed lag case. It omits error/auth/rate-limit behavior, but for a public read-only ECB feed that gap is minor.

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?

Front-loaded with the core purpose, then the behavioral nuance. Two sentences, no filler. Slightly dense in the second sentence with multiple clauses, but each 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?

An output schema exists, so return values need not be spelled out, and the description complements it by explaining the non-obvious substitution semantics that would otherwise be surprising. The only real gap is the absence of explicit sibling routing guidance.

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% and all three parameters (base, date, symbols) are documented there with defaults and ISO 4217 formats, so baseline 3 applies. The description adds no parameter-level detail beyond the schema, though it does clarify output semantics tied to the date parameter.

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 first sentence states a specific verb+resource: 'ECB reference rates for one base currency on a specific date.' An agent can distinguish this from latest_rates and rate_timeseries on the date-scoping axis, though no sibling is named explicitly.

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?

Usage is implied rather than stated — the historical/dated nature of the lookup points at this tool over latest_rates, and the weekend-substitution rule tells the agent what happens at the edges. But it never explicitly says when to prefer this over rate_timeseries or convert, leaving routing to inference.

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

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

With no annotations, the description carries full behavioral burden and does disclose useful traits: one rate per requested currency or all tracked currencies when symbols is omitted, the presence of a rate_date, ECB working-day publication, and a note field for lagging currency feeds. It does not cover error behavior or authentication, but for a public reference-rate lookup the disclosed behavior is substantial.

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 core resource and scope, then efficiently adds return-shape and publication caveats. Every sentence earns its place, with no redundant or filler language.

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 simple two-parameter lookup with an output schema and no annotations, the description supplies enough context to invoke the tool correctly. It explains the default scope when symbols is omitted and the working-day publication caveat, while the output schema handles detailed return structure.

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. The description adds only limited parameter context, reiterating that symbols omitted returns all currencies and that base is a single currency, both of which the schema already documents.

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 the specific resource (latest published ECB reference rates) and scopes it to one base currency. It implicitly distinguishes itself from siblings like historical_rate and rate_timeseries by emphasizing 'latest published,' and from convert/list_currencies by describing a rate snapshot rather than conversion or currency enumeration.

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 by 'latest published' and the sibling set, but the description does not state when to use this tool instead of historical_rate, rate_timeseries, convert, or list_currencies. There are no explicit exclusions or alternative-routing instructions.

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

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

With no annotations, the description carries the burden and does disclose the salient behavior: it is a read-only enumeration limited to euro-tracked currencies, with a concrete return example. It stops short of noting that the list is static or whether any auth/rate constraints apply, but for a zero-argument lookup the disclosure is largely sufficient.

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?

Three short, front-loaded sentences: scope, return shape, and intended use, with no filler. The inline JSON example earns its place by pinning the exact field names.

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 zero-parameter lookup with an output schema that already defines return values, the description supplies everything else an agent needs: what the list contains, the shape of an entry, and when to call 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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; the baseline for a parameterless tool applies. The description's mention of codes and names relates to output, not input, which is already covered by the output schema.

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 resource with scope ('The ISO 4217 currencies Frankfurter tracks against the euro') and states exactly what is returned ('each currency's code and name'), so an agent can distinguish it from convert/latest_rates without opening a schema.

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 gives an explicit use case: 'check whether a currency code is valid before calling the other tools.' This routes the agent correctly relative to the sibling rate/convert tools, though it does not name which siblings consume the codes or state when the tool is unnecessary.

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

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

With no annotations, the description carries the full burden and does well: it discloses the per-working-day granularity (implying holiday gaps), the min/max/average aggregation, and two refusal conditions that never reach upstream. It stops short of stating the configured maximum range length or whether errors are returned as structured failures.

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?

Front-loaded with the resource definition, then returns, then failure behavior — a logical order with no filler. Length is appropriate for the amount of information conveyed, though the last clause could be tightened.

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?

An output schema exists, yet the description helpfully pre-summarizes the response shape (per-day points plus aggregates), and it covers the invalid-input paths. The only meaningful omission is the actual value of the configured maximum range, so the agent cannot self-check before calling.

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 all four parameters including ISO 4217 formatting and the 366-day constraint are already documented. The description only adds the framing that base/symbol form 'one currency pair', which is a marginal gain over the schema baseline.

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?

Names a specific resource and scope: the ECB reference rate for one currency pair over a date range. An agent can distinguish it from latest_rates and historical_rate by the range framing, but the description never names those siblings to make the boundary explicit.

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?

Usage is implied by 'across a date range' — use this instead of a single-point lookup when a series is wanted. However, no alternative is named and no when-not-to-use condition is given beyond the internal validation rules (range too long, start after end), which are error handling rather than tool selection guidance.

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