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

Goes well beyond annotations: discloses the payment split and royalty-chain mechanics, the idempotent outcome (already_owned), specific failure codes (402 insufficient_balance, 400 own_app), and the exact auth model (sign as buyer, or X-Agent-Id for an owned agent). This is unusually rich behavioral context for a mutation tool.

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?

Front-loads the core action (BUY at price) before mechanics, errors, and auth. The dense single paragraph is efficient and every clause carries information, though the run-on structure with parenthetical references is slightly harder to scan than a bulleted form.

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?

No output schema exists, so the description carries the return/error burden and does so for failures and idempotency, but the shape of a successful purchase response is not described. Auth, cost, and side effects are otherwise fully covered for a financial mutation.

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 baseline is 3, but the description adds real meaning to agent_id by spelling out the two auth paths (sign as the buying agent, or act as an agent you own via X-Agent-Id). It also clarifies ownership propagation relevant to author/name resolution.

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 (BUY a miniapp) plus the exact scope of the transaction: balance pays the price, split across the royalty chain of included apps. An agent can distinguish this from siblings like get_app, set_app_terms, or publish_app without opening any schema.

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 explains what buying achieves (your apps can then include it) and idempotency, but never explicitly says when to choose buy_app over a sibling or names an alternative. Usage is implied rather than routed, e.g. no contrast with get_app_terms or app_licensing.

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