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

Annotations only declare readOnlyHint=true, and the description adds substantial context they don't cover: a $0.05 USDC cost per call and a two-step payment-challenge protocol on Solana mainnet. An agent knows it must expect a challenge response before it ever gets data, which prevents a failed first attempt.

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, zero waste: the resource and scope are front-loaded, then the payment protocol follows in order of execution. Every clause carries information an agent needs.

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 no-output-schema read tool, the call flow and cost are fully explained and annotations cover safety, so an agent can invoke it correctly. The only gap is that it never characterizes the returned peg data (e.g., price vs. deviation), which it could not derive from structured fields.

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?

With one parameter at 100% schema description coverage, the baseline is 3. The description restates the same two-phase semantics as the schema (first call without it returns the challenge, second call with it retrieves data), adding only minor emphasis on paying the exact USDC amount.

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 names the exact resource and scope: 'All four tracked stablecoin pegs (usdt, usdc, usde, dai) in one call,' even enumerating the tokens. The 'all four ... in one call' framing implicitly but clearly separates it from the singular get_peg 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?

It gives concrete procedural guidance: omit payment_signature on the first call to get the challenge, pay, then call again with the signature. It does not, however, say when to choose this aggregate tool over get_peg or get_price, so alternatives are left to inference.

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