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

Annotations only declare readOnlyHint=false and idempotentHint=false; the description goes well beyond by stating it charges nothing, holds no funds, that the lock lasts quote_ttl_seconds, and that one quote buys once (which grounds the non-idempotent hint). It also previews the precheck results returned, so the agent knows the call surfaces funding and mandate viability.

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-loaded with the core action, then sequencing, then return shape, then constraints — a logical order with no filler sentences. The trailing example is largely redundant with the schema's product_id example, which is the only mild waste.

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 the description compensates by enumerating the return fields (quote_id, product, price, expires_at, mandate_precheck, wallet_precheck, refund_terms, next-step hint). Combined with the side-effect and TTL disclosures, an agent has everything needed to invoke this correctly and interpret the result.

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 parameters are fully documented in the schema, and the description's example ({product_id: "wh1-5838281"}) duplicates the schema's own example rather than adding new meaning. Baseline 3 applies since the schema does the heavy lifting and the description adds little parameter-level detail beyond tying product_id to search_plans.

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 ('Lock the final price of one plan for a short time'), and its scope is immediately distinguishable from search_plans (which finds plans) and purchase (which actually buys). An agent can route between the three siblings from the description alone.

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?

Explicit sequencing guidance: 'Use it after search_plans, with a product id from its results, and before purchase.' It also points to get_policies for the lock duration, naming the alternative source of that information rather than leaving it implicit.

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