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

With readOnlyHint already declaring the safety profile, the description adds real behavior: the dual endpoint routing (Search vs plain GET), the constraint that field_name and field_value must be supplied together, and the UPPER_SNAKE field-naming convention including custom fields like Industry__c. It stops short of describing pagination semantics or result shape beyond the count_total mention.

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?

A single dense paragraph that front-loads the core action before the routing detail; nearly every clause carries information. It is slightly packed with the endpoint paths, but no sentence 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 an 8-parameter listing tool with no output schema and a fully documented input schema, the description supplies the endpoint routing, filter pairing rule, and field naming plus the count_total response note. The main gap is that return shape and pagination behavior (top/skip interaction) are left implicit.

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 coverage is 100%, so the baseline is 3, but the description genuinely adds meaning: the pairing requirement for field_name/field_value, the accepted field-name format, and the custom-field example Industry__c. That goes beyond the schema's terse per-parameter text.

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 gives a specific verb (list/search) and resource (records of one of eight named types), and enumerates the exact object enum values, so the agent knows precisely what it operates on. It does not, however, differentiate itself from siblings like insightly_get_record or insightly_search_by_tag, which also retrieve records, leaving that routing to inference.

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 clearly states the conditions that switch the tool between search and plain listing: field_name + field_value (both required together) or updated_after_utc selects GET /<Object>/Search, otherwise GET /<Object>. This is strong conditional guidance, but it never says when to prefer this tool over insightly_search_by_tag or insightly_get_record.

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