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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the description goes further with substantive behavioral context: the underlying data source (ECB daily euro reference rates), its limited 30-currency coverage, the close-based-only constraint, and the informational/no-signals caveat. This is exactly the kind of context annotations cannot express.

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?

Purpose and triggering conditions are front-loaded, and each subsequent sentence carries distinct information (valid inputs, data-source limits, return shape, disclaimer). It is dense but every clause earns its place; the indicator list and coverage caveat are the only slightly redundant parts.

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?

Although an output schema exists, the description still conveys the return shape (latest value plus a short series, with source and last rate date) and the domain limits (ECB-only currencies, close-based indicators) that an agent needs to avoid misleading callers. Nothing material is missing for correct invocation.

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 the schema already documents symbol format, defaults, ranges and enums. The description nonetheless adds usable guidance: symbol as two ISO codes, interval default of 1d, the specific indicator set this tool supports, and which indicators are unsupported here. Only minor overlap keeps it just above the 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?

The opening sentence gives a specific verb and resource ("Calculates indicators for a currency pair"), and the body explicitly distinguishes this tool from its sibling compute_indicators based on data source and asset class. An agent can tell them apart without opening either 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 states the trigger condition (user names a currency pair and asks for indicators) with concrete examples ("RSI and MACD for EUR/USD", "50-day SMA for USD/JPY on the weekly chart"), and names the alternative and its condition (stocks, crypto, atr, stochastic, vwap → compute_indicators). When-to-use and when-not-to-use are both explicit.

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