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

The annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds the underlying API route (POST /v3/customer/email/search), which is mildly useful, but does not describe return behavior, no-match handling, or pagination. With annotations covering safety, this is a reasonable but thin extra layer.

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 short sentences with the primary action front-loaded and the API route trailing as secondary metadata. Every part earns its place and nothing is wasted.

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 lookup with full parameter coverage and readOnlyHint, the description gives enough to call the tool correctly. It does not explain result shape or no-match behavior, and there is no output schema, but those gaps are minor for this tool's complexity.

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 the important semantic that the tool matches customers who own 'any of the given email addresses', clarifying OR semantics across the array beyond the schema's generic 'Email addresses to look up'. The excludeCustomerId parameter is not described, but the schema already documents it.

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 states a specific verb ('Find'), resource ('customers'), and scope ('by email addresses'), and the sibling tools include find_customers_by_phone and search_customers, so the distinction is clear. An agent can identify this as the email-based customer lookup 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?

The description implies usage when email addresses are available, which is adequate context. However, it does not explicitly name when to prefer this over search_customers or find_customers_by_phone, nor does it state any exclusions or prerequisites.

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