textokit_fx_rates

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

No annotations are provided, so the description bears the full load — and it does disclose the critical non-obvious trait: this is a paid call at 0.001 USDC via x402 on Base, charged to the caller's wallet, with a free sample as alternative. That is genuinely valuable. However, it says nothing about the response shape, rate timestamp/date semantics, or error behavior when a currency code is unsupported, which matter for a data-fetch 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?

Three short sentences with the resource named first, followed by cost and the free alternative — a sensible front-loaded order. No filler, though the currency list in sentence one partially duplicates what the schema already conveys.

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 two-parameter, no-output-schema tool, the essentials (what it returns conceptually, what it costs, how to try it free) are present. What is missing is anything about the returned data's freshness, date coverage, or failure modes, which the agent would need to decide between this and the free/alternative rate tools.

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% — both 'base' (default USD, ISO 4217) and 'quotes' (comma-separated, 1–20 codes) are fully documented in the schema. The description reinforces supported currencies but adds no syntax, default, or limit detail beyond what the schema already says, so the baseline 3 applies.

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 resource (daily FX exchange rates) and enumerates representative currencies, so an agent immediately knows this is the currency-rate tool rather than a crypto or Argentina-indicator one. It does not explicitly name the sibling tools it displaces (textokit_crypto_prices, textokit_dolar_ar, textokit_bcra_indicadores), so the differentiation is implied rather than stated.

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 context is implied by 'daily exchange rates' and the pointer to textokit_sample as a free trial, which is a useful fallback route. But there is no explicit when-to-use/when-not, no guidance on choosing between this and the overlapping siblings (dolar_ar, bcra_indicadores, crypto_prices), and no note on freshness or historical coverage.

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