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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds genuinely new behavior: results are ordered newest-first, default page size 25 with a ceiling of 100, and the cursor must be the prior response's next_cursor. It also flags the non-obvious data caveat that phone numbers are returned as stored and only mobile_number can receive texts. Missing only return-volume or total-count behavior.

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 dense sentences, front-loaded with what is returned and then how to page; almost every clause carries information. Minor waste in repeating the limit default and cursor name that the schema already documents.

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, no-output-schema list tool, the description covers filtering, ordering, page sizing, cursor round-trip, and a data quirk about phone numbers. The remaining gap is the shape of a returned customer record beyond 'contact details', which an agent would have to discover by calling.

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 all three parameters are already documented, and the description largely restates them (search fields, 25 default, up to 100, next_cursor as cursor). It adds little semantic detail beyond the schema, so the baseline of 3 applies.

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?

States a specific resource (customers of the company with contact details) and the searchable fields, which lets an agent tell it apart from the sibling list_employees / list_invoices tools by resource alone. It never explicitly names what it is not, so it stops short of perfect clarity.

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?

Gives operational guidance (search by name, email, phone or address; paginate with cursor) and implicitly signals this is the lookup tool for customer records. There is no explicit when-to-use/when-not statement or reference to an alternative tool for a different retrieval shape.

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