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

Annotations already mark this as read-only and non-destructive. The description adds useful behavioral context beyond that: it requires a connected store/plan tier, reports own buy-box and undercut status, and changes behavior based on whether ASIN is provided. No contradictions with annotations.

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 information-dense but not bloated: it front-loads the core purpose, then covers parameter-dependent behavior, requirements, and typical user intents. Every sentence contributes useful guidance, and the formatting makes the two modes easy to distinguish.

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 read-only tool with no output schema and two optional parameters, the description is complete: it explains input modes, output fields, prerequisites, and use cases. An agent can determine when to invoke it and what to expect without needing additional schema or annotation details.

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 documents both parameters. The description adds meaning beyond the schema by explaining that the optional ASIN must come from the seller's catalog and that omitting it switches the tool to a 'most-contested products' mode, which is essential for correct usage.

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 identifies the tool's function: showing competitors on the seller's own products, with a specific verb-like framing in 'Who's competing'. It also distinguishes scope by emphasizing 'OWN products' and details the output fields (buy-box winner, FBA/FBM, price, tenure), which separates it from generic competition tools.

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 gives explicit usage scenarios: pass an ASIN for a listing-level competitor list, omit it for the most-contested products, and provides concrete example queries like 'am I losing the buy-box'. It also states a prerequisite (connected store, Starter+), though it does not name alternative sibling tools for comparison.

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