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

Annotations already declare readOnlyHint, idempotentHint and closed-world behavior, so the safety bar is lower. The description adds genuinely new context beyond them: 'Free' and 'Creates no payment' tell the agent there is no charge or payment side effect, which is the key behavioral fact for a price-comparison tool. It does not discuss what happens when the budget excludes all services.

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?

Three short sentences, front-loaded with the 'Free' fact and the core action. The enumeration of task categories is somewhat redundant with the schema enum, but it is compact and readable rather than padded.

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?

With only two parameters, an output schema, and full annotations, the description covers what the tool does, that it is free, and that it takes an optional budget. The only meaningful gap is fallback behavior when no service matches the task/budget, which is a minor omission given the output schema exists.

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 50%: max_usdc is documented in the schema and the description reinforces it ('compares the published per-call price with an optional budget'). The task parameter has no schema description, and the description's list of categories largely restates the enum values, adding only human-readable labels such as 'daily reports' for 'daily_report'.

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 states a specific verb and resource ('Choose a Diamond tool') and enumerates the task categories it routes over, which matches the enum in the schema. It is clearly a recommendation/selection tool rather than a data-fetching one, though it does not explicitly contrast itself with siblings like diamond_catalog or search.

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?

Usage is implied: an agent should call this to pick a Diamond service by task and price before invoking it, and the budget comparison hints at pre-purchase decision-making. However, no sibling is named as an alternative and there is no explicit when-not guidance (e.g., what to do if nothing fits the budget).

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