qm_buy

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

With no annotations, the description carries the full behavioral burden and does so excellently: it states that the tool NEVER pays, NEVER handles private keys, and NEVER holds funds, and clarifies that the agent signs and submits from its own wallet while the rail fulfills automatically. This prevents the agent from assuming it is making a payment or handling keys.

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 longer than average but every sentence earns its place: core purpose, input rules, payment format, safety behavior, and examples. The most important safety/selection facts are front-loaded before the examples.

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 and no annotations, yet the description explains what is returned (exact payment requirements, amounts in USDC smallest units, step-by-step instructions), how payment works, and what the agent must do. The examples cover both endpoint types, leaving no critical gap for invoking the tool correctly.

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. The description adds value by explaining the exactly-one-of constraint across sku and endpoint, mapping each endpoint to required params, giving price ranges, and providing concrete examples showing valid combinations.

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 a specific verb (Get), a specific resource (the live 402 payment challenge for one purchase), and the two input paths (sku vs endpoint). This makes its purpose unmistakable and clearly distinct from sibling data-retrieval tools like qm_data_iss_pass or qm_catalog.

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 explicitly tells the agent to pass exactly one of sku or endpoint, and explains which parameter pairs with which endpoint (lat/lon for iss-pass, url for summarize). It does not explicitly name sibling tools as alternatives, but the selection criteria for this tool are complete and unambiguous.

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