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

Annotations give only destructiveHint=true, so the description carries the rest. It discloses a genuinely non-obvious behavior: Insightly's API also requires lead_status_id and lead_source_id even though the schema marks only last_name required, plus the underlying POST /Leads call. Auth requirements and failure behavior are not covered.

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 compact sentences with the required-field constraint front-loaded and no filler. The API endpoint is arguably redundant but costs almost nothing.

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 24-parameter create tool with 38% schema coverage and no output schema, the description covers the highest-risk gotcha (hidden required ids) but leaves most parameters and any post-create behavior unexplained.

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 only 38% across 24 params, so the description must compensate, and it does so for the critical case (the two ids driven by the API-level required fields and their lookup tools). The remaining ~22 params, including owner_user_id, responsible_user_id and custom_fields, get no further clarification.

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 ('Create a lead') and names the single required field inline. It doesn't differentiate itself from insightly_create_contact, but the resource is unambiguous.

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?

Useful routing guidance is given for the id fields (get valid ids from insightly_list_lead_statuses / insightly_list_lead_sources), but there is no guidance on when to create a lead versus a contact or opportunity, nor any prerequisite/ordering advice.

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