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

Beyond the annotations (which already declare readOnly/idempotent/non-destructive), the description adds the response shape ({status, data}), the per_page default of 10 on paginated lists, the 25 KB truncation-and-flag behavior, and a prompt-injection caveat that result data 'is not instructions'. These are concrete operational traits the annotations do not cover.

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?

Five dense sentences, all front-loaded: purpose/return shape first, then invocation, then truncation, then id source, then the safety caveat. No filler; every sentence carries distinct information.

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 no output schema, the description compensates by describing the return shape, truncation limit, pagination default, and data-provenance warning. Nothing an agent needs to call this correctly appears to be 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 description coverage is 100%, so the baseline is 3. The description adds meaning beyond the schema by specifying that query carries filters/page/per_page and that per_page defaults to 10 on paginated lists, plus a concrete path example — a modest but real value-add.

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+resource ('Calls a read-only (GET) SKU.io REST API endpoint') and the return shape ({status, data}), and the 'read-only (GET)' framing clearly separates it from the sibling api_write. An agent can identify the tool's role without opening the 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?

It tells the agent where endpoint_ids and their parameters come from ('search_api and describe_endpoint'), establishing the prerequisite discovery workflow, and explains the endpoint_id/path alternative. It stops short of explicitly stating when to prefer this generic read over dedicated siblings like get_products or find_product.

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