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

Annotations already declare the tool safe (readOnlyHint, idempotentHint, non-destructive). The description adds behavioral context beyond annotations by specifying that results include 'product counts' and that output can be 'optionally filtered by country,' which are not evident from annotations or the schema alone.

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 well-structured with distinct sections (tool_description, when_to_use, combination_hints, output_format). Each sentence adds value: the combination hint with nexbid_search is especially useful. It is compact without unnecessary verbosity, though the XML-style tags add slight overhead.

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 simple read-only list tool with one optional parameter and no output schema, the description is complete. It explains what the tool returns ('list of categories with product counts'), the optional country filter, and when to use it relative to nexbid_search. No critical information appears missing.

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% (the geo parameter has a full description). The description does not add much beyond the schema—only says 'Optionally filter by country,' which mirrors the schema. Since the schema already documents the parameter thoroughly, a baseline score of 3 is appropriate.

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 the tool's function: 'List all available product categories in the Nexbid marketplace with product counts.' It identifies the resource (categories), the action (list), and the scope (Nexbid marketplace), and distinguishes it from sibling tools like nexbid_search by positioning it as a pre-search exploration step.

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 usage guidance is provided: 'When user wants to explore what is available before searching. Use BEFORE nexbid_search to help narrow down the query.' This directly states when to use it and names the alternative tool, giving clear context for tool selection.

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