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

Annotations already declare readOnly/idempotent/non-destructive, and the description usefully confirms the safety profile in domain terms ('free and never spends funds') and enumerates the settlement rails a plan may target. It omits operational detail such as whether quotes expire or how failures surface, so it adds context but not exhaustively.

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, no filler. The selection behavior and payment rails come first and the free/no-spend guarantee is held to the final clause, so the highest-value information is front-loaded.

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 read-only, idempotent quoting tool with no output schema, the description covers the essential safety and rail context but says almost nothing about the shape of the returned 'executable purchase plan' that the agent must act on, nor about the zero-result or over-budget case. Adequate but with a clear gap.

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 description coverage is 0%, so the description carries the burden, and it does clarify the intent of goal and max_price_usd ('hard USD budget'). However it lists only four rails while the preferred_rail enum also includes direct_solana_sol, and it never mentions the x402 default, leaving meaningful parameter detail undocumented.

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 ('select one product and return an executable purchase plan') and scopes it with the inputs that drive the selection (agent goal, hard USD budget). The closing line 'never spends funds' cleanly separates it from the execute_paid_product sibling, so an agent can route between quoting and executing without opening either 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 establishes the precondition for use (an agent goal plus a hard USD budget) and implies the planning phase precedes execution by stating the tool is free. It never explicitly names execute_paid_product as the follow-up or states when not to use it, so the routing is inferable rather than spelled out.

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