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

The readOnlyHint annotation already establishes that this is a safe read operation. The description adds useful behavioral context beyond annotations: criteria are AND-combined, pagination uses offset/limit, and next_offset indicates where to continue.

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 front-loaded with purpose, filtering behavior, and the key alternative. The field list and endpoint are somewhat extra but still useful; overall it is appropriately sized and structured.

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?

Given the rich schema and readOnly annotation, the description covers the main call behavior: filtering, paging, useful fields, and an alternative tool. It does not fully describe the response shape beyond next_offset, but it is complete enough for an agent to invoke the tool correctly.

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 schema already documents limit, offset, criteria, order_by, and search_state in detail. The description reinforces AND logic and pagination but adds little parameter meaning beyond what the schema provides.

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 and resource: search contacts, explicitly covering people and companies. It also names the sibling rex_autocomplete_contacts for a narrower name lookup, so the agent can distinguish this tool from alternatives.

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?

It explains that criteria combine with AND and that results are paged with offset/limit and next_offset. It also gives an explicit alternative condition: to find someone by name, use rex_autocomplete_contacts instead.

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