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

Annotations only say readOnlyHint=false and destructiveHint=false, which is thin. The description goes well beyond that: it names the external recipient (CurrencyGuard) that will receive the user's provider and optional email, requires an explicit consent step and a plain disclosure to the user, and imposes a hard one-call-per-conversation cap. Those are exactly the behavioral traits 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?

The purpose is front-loaded and every clause carries an instruction, but the consent and email rules are spread across several short sentences with some restatement (optional email, no address means no reply). Slightly denser than needed, though no sentence is truly filler.

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?

There is no output schema, so explanation of return values is not required. With three params, one required, an external-recipient disclosure, and consent/rate-limit rules fully spelled out, an agent has everything it needs to call this correctly and safely.

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 already 100%, so baseline is 3, but the description adds real meaning: provider alone is a complete enquiry, email is optional and needed only if the user just offered it, and an email must never be carried over from earlier in the conversation. That materially changes how the optional email parameter should be populated.

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: find out whether Guards can be bought through a given payment provider or bank, and explicitly ties a Guard purchase to a payment provider. This is clearly distinguishable from siblings like price_guard, price_guard_extension, and get_spot_rate, which price rather than answer availability questions.

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?

Gives explicit when-to-use and when-not-to-use rules: ask the user first, call only after they say yes, never call more than once per conversation, and never call after the user declines. That is about as complete a routing/eligibility rule set as a tool description can carry.

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