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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower; the description still adds real context by naming the pricing source (Chainlink oracle on Base) and stating 'Free, no key needed', which removes an auth question the agent would otherwise have to guess at. It omits freshness/staleness and rate-limit behavior, which matters for price data, keeping it at a 4.

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, front-loaded with the resource and its scope, followed by routing and cost information. Every clause carries decision-relevant content and nothing is repeated from the schema or annotations.

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?

Covers what it returns conceptually, which sibling to fall back on, and the auth/cost model, which is enough for a 4-parameter read-only lookup with a fully documented schema. The one remaining gap is that callers can't tell what the response looks like (quote plus timestamp? single value?) since there is no output schema.

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 baseline is 3, but the description adds the kind-to-parameter mapping that the schema only implies: tickers ('crypto/metal') versus a currency pair ('exchange rate between two currencies'), which tells the agent that fx uses base/quote while crypto/metal use symbol. Concrete examples of tickers appear in the schema, not duplicated here, so no waste.

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 and resource ('Current price of a major cryptocurrency, gold or silver ... or an exchange rate') and bounds the scope to well-known assets and two named data families (Chainlink on Base, fx pairs). The qualifiers 'major' and 'well-known assets' implicitly separate it from get_token_price's long-tail coverage, and the pointer to list_price_symbols distinguishes it from the symbol-discovery sibling.

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?

'Use for quick quotes of well-known assets' gives a positive usage condition, and 'call list_price_symbols when unsure a symbol is covered' names an alternative with the condition that selects it. It stops short of saying when NOT to use it (e.g. obscure tokens where get_token_price is the right sibling), so it is strong but not exhaustive.

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