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

readOnlyHint=true already covers the safety profile, but the description adds real behavioral context beyond annotations: which endpoint is invoked under which parameter combination, and the pairing constraint on field_name/field_value. It omits pagination/return-shape behavior, keeping it short of a 5.

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?

Three dense sentences, front-loaded with the resource and record types before the filtering mechanics. Every clause carries information, though the examples list is slightly long.

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 read tool with no output schema, the description covers purpose, both query modes, and field-name syntax adequately. Return-shape details (e.g. what count_total produces) are delegated to the schema, which is acceptable here.

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 baseline is 3, but the description adds value the schema lacks: the UPPER_SNAKE field-name convention with concrete examples (EMAIL_ADDRESS, LAST_NAME) and custom-field syntax (Industry__c), plus the both-or-neither rule for field_name/field_value.

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 and resource and enumerates exactly which record types are supported (Contacts, Organisations, Leads, etc.). It also distinguishes the two operational modes — filtered search vs plain list — which no sibling does.

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?

Clearly explains the condition that selects each mode: field_name+field_value (required together) or updated_after_utc triggers /Search, otherwise plain GET. It does not, however, name alternatives such as insightly_search_by_tag or insightly_get_record for single-record lookups, so the when-not guidance is incomplete.

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