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

Annotations already declare readOnlyHint=true, and the description adds valuable behavioral context: it returns one row per entry, and unresolved entries come back as error rows instead of failing the call. This goes beyond the annotation by explaining error handling and output structure.

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?

Two sentences front-load the purpose and cover usage, output format, and error behavior without redundancy. Every sentence earns its place, making it efficiently concise.

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 2-parameter read-only tool with no output schema, the description is complete: it explains input constraints, return row structure, and error handling. No important behavioral aspects are omitted.

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 schema already describes both parameters. The description adds the crucial semantic that the caller must provide either names or itemIds, and implies mutual exclusivity. It also clarifies the per-entry output fields, adding value beyond 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 the tool compares latest Grand Exchange prices for up to 10 items in one call. This distinguishes it from single-item tools like get_item_price or lookup_item by emphasizing the batch comparison use case.

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 tool's context ('up to 10 items in one call') and provides the key usage instruction to provide either names or itemIds. It does not explicitly name alternatives or state when not to use it, but the batch context makes the intended usage clear.

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