List Merchant Center accounts

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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive hints. The description adds useful behavioral context: it lists accessible accounts, returns a specific structure, includes pagination via nextPageToken, and gives a filter syntax example. This goes beyond the annotations without contradicting them.

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?

Three sentences, each earning its place: purpose, return structure, and usage guidance. Front-loaded with the primary verb and resource. No fluff or redundancy.

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?

Despite having no output schema, the description compensates by listing the exact return fields and nextPageToken. It covers authentication scope, pagination, filter syntax, and the typical first-step use case. Slightly less complete than a perfect list tool description because it omits error scenarios or default page size, but the schema already provides limits.

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 descriptions cover 100% of the three parameters (filter, page_size, page_token) with examples and constraints. The description repeats the filter example but adds no new semantic detail beyond the schema. With full schema coverage, the baseline is 3, and no additional value is provided.

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?

Clear verb 'Lists' with specific resource 'Merchant Center accounts'. The description names the returned fields and nextPageToken, and explicitly distinguishes this tool from siblings by stating it is the first step to discover the account ID other tools need.

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?

Provides explicit when-to-use guidance: 'Use it first to discover the account ID the other tools need'. Also mentions an alternative (setting GOOGLE_MERCHANTS_ACCOUNT_ID once). However, it doesn't explicitly mention when not to use it or name alternative sibling tools, so it falls short of a 5.

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