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

Annotations indicate readOnlyHint=false, destructiveHint=false, and openWorldHint=false, but the description goes beyond by revealing the payment requirement (x402), network isolation, and the specific meta fields ('_meta['x402/payment']' and '_meta['x402/payment-response']'). It also states no account/API key needed, which is useful context.

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 critical paid execution flow, then adds the pricing details and feedback channel. It is concise given the complexity, but the feedback part could be seen as extra; still, it earns its place by clarifying how to escalate issues.

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 complex paid execution tool, the description covers the crucial payment flow, sandbox isolation, and return fields. It doesn't explain error cases beyond the payment required, but it references 'GET /quote' and service_card for runtime listings. Given no output schema, it could explain stdout/stderr format more, but it's adequate.

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 documents all parameters. The description adds minimal parameter-specific semantics, but it does mention that 'limits' affect the price and that 'runtime' can be looked up via quote or service_card. This slightly exceeds 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 description clearly states the tool runs code in an isolated sandbox and returns stdout, stderr, and exit code. It uses a specific verb ('run') and resource ('code'), and distinguishes itself from siblings like search_listings and service_card by its paid execution model.

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 two-step usage: call once to get a price, then call again with a signed payment. It tells the agent to use 'service_card' to list runtimes and 'GET /quote' for pricing. It also explains the feedback mechanism as an alternative for complaints/questions.

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