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

The annotations already state readOnlyHint=true and openWorldHint=false, so the read-only, closed-world behavior is covered. The description adds useful context about the data source (mail history) and the contact fields available, but it does not discuss limits, result ordering, or other operational details beyond the output schema.

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 a single front-loaded sentence with no wasted preamble. The parenthetical field list is dense but informative, and the core purpose is stated first.

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?

The tool is simple (2 optional parameters), has annotations, and has an output schema. The description covers the data source, matching behavior, and returned fields, which is sufficient to select and invoke the tool. Minor gaps around pagination/default limit behavior are acceptable given the schema and output schema.

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 0%, so the description must compensate. It usefully explains that matching applies to name, address, or domain, which clarifies the query parameter. However, it provides no semantic detail for the limit parameter or for query length/optionality beyond what the schema itself shows.

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 resource (contacts from mail history) and what is matched (name, address, domain), plus the fields returned. It distinguishes itself from search_emails by domain, but it does not explicitly name or contrast with sibling 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 matching fields imply that this tool should be used to find contacts by name, address, or domain. However, there is no explicit guidance on when to use it instead of search_emails or other sibling tools, and no exclusions or prerequisites are stated.

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