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

readOnlyHint=true already tells the agent this is a safe, non-mutating read, so the description needn't restate that. It adds the GET /contacts endpoint context, which is mildly useful for parity with the Freshdesk REST docs, but says nothing about pagination behavior, result ordering, or limits beyond what the schema already declares.

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 no filler, and the core purpose is front-loaded ahead of the API reference note. The endpoint sentence earns its place only modestly, but there is no wasted prose.

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 read-only list tool with zero required params and a fully documented schema, the description is barely sufficient: an agent can call it, but it lacks any statement of return shape, default sorting, or pagination semantics, and no output schema exists to fill that gap. The missing list-vs-search routing against freshdesk_search_contacts is the most consequential hole.

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 eight filters (page, per_page, email, phone, mobile, state, company_id, updated_since) are already documented with types, ranges, and enum values. The description's bare 'filter' wording adds no syntax, combination, or precedence guidance 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 verb plus resource ('List/filter contacts') that an agent can act on immediately, and the REST endpoint reference reinforces what it maps to. It stops short of distinguishing itself from the sibling freshdesk_search_contacts, so an agent still has to guess which of the two list/search tools it wants.

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?

There is no when-to-use guidance and no mention of alternatives. The most important omission is freshdesk_search_contacts, which overlaps heavily with 'List/filter contacts'; nothing in the description says when to prefer this endpoint over that one, or when the filters here are insufficient.

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