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

Annotations already indicate readOnlyHint, openWorldHint, idempotentHint, and non-destructive. The description adds 'Read-only; baseCurrencyId and quoteCurrencyId are canonical ids and amount is the quantity to convert. No API key required.' It also warns in the parameter description that passing 0 returns a 0-valued response. This adds useful behavioral context beyond annotations, and nothing contradicts them.

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 purpose and examples in the first sentence. The second and third sentences add critical usage distinctions and parameter context. Every sentence earns its place; there is no fluff or repetition. At ~80 words, it is concise and well-structured.

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?

Given the tool's moderate complexity (4 parameters, 3 required), 100% schema coverage, and full annotations, the description covers key aspects: purpose, usage examples, contrast with sibling, parameter constraints, and idempotency/read-only nature. Without an output schema, it doesn't need to detail return format. The description is complete and leaves no critical ambiguity.

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. However, the description adds significant value: it explains that 'baseCurrencyId' and 'quoteCurrencyId' are CoinPaprika slugs and that symbols like 'BTC' are rejected. For 'amount', it clarifies the default of 1 and warns about passing 0. The 'rationale' parameter is also explained with examples and usage notes. These additions go well beyond the schema descriptions.

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 clearly states it converts an amount from one crypto or fiat to another at the current rate, with examples ('0.5 BTC in USD', '100 USDC to EUR'). It distinguishes itself from sibling getTickersById by specifying that tool is for 'plain coin price without an amount'. The purpose is specific, actionable, and well-differentiated.

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 explicit when-to-use (for conversions with an amount) and when-not-to-use (plain price, use getTickersById). It gives concrete examples of valid calls and clarifies that no API key is required. This gives the agent clear context for selecting the tool over alternatives.

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