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

The description adds behavioral context beyond annotations by detailing the internal steps ('resolves items, computes total weight, quotes couriers') and explicitly reinforces safety ('Read-only, side-effect-free'). While annotations already declare readOnly and non-destructive, the description adds functional richness about what the widget computes and returns. It does not describe error handling, but that is a minor gap given the strong annotation coverage.

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 extremely concise: one sentence explains the functional purpose and a second sentence confirms side-effect-freedom. Every word earns its place, with no redundancy or filler. It is also front-loaded with the primary action, making it easy to scan.

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 4-parameter tool with no output schema, the description adequately conveys the main output (a widget with weight and courier quotes) and the process. It does not explain the exact return structure or error scenarios, but the combination of annotations, schema descriptions, and the description's functional breakdown makes the tool understandable. A complete 5 would require mentioning output fields or potential failure modes, but the description is sufficient for a read-only aggregation widget.

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 100%, so the parameters are already well-documented. The description adds no additional parameter-level semantics beyond what the schema provides (e.g., it implies 'items' are product IDs and quantities, but schema already states this). Baseline of 3 is appropriate as the description does not hinder but also does not enrich the schema.

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 clearly states what the tool does: it 'combines catalog stock/weight data and a live shipping quote into one widget' and specifies the actions ('resolves items, computes total weight, and quotes couriers'). This distinguishes it from siblings like quote_shipping or query_catalog by focusing on the preparation workflow, not just quoting or data lookup.

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 implies the use case: when a user needs to prepare a shipment, combining catalog data with shipping quotes. It doesn't explicitly name alternatives or exclusions, but the context is clear and distinct from sibling tools. A slightly higher score would require explicit 'use when vs. instead of' guidance.

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