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

Annotations already declare destructiveHint=true, so the safety signal is supplied structurally; the description adds nothing about side effects, required permissions, or whether the create is idempotent. A bare 'POST /Opportunities' restates structured information rather than adding behavioral context such as the impact of custom_fields or field validation 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 short sentences, front-loaded with the action and constraint. Nothing is padded, though the parenthetical requirement note duplicates the schema's 'required' declaration and thus earns little.

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 13-parameter creation tool with no output schema and no annotations beyond a destructive hint, the description is too thin: it says nothing about the created record, which fields are commonly needed (e.g. organisation_id, owner_user_id), or the effect of omitting optional fields. The rich schema partly compensates, but the description itself leaves notable gaps.

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 85%, so the schema itself documents virtually every field including formats like the UTC date string and custom_fields semantics. The description only repeats that opportunity_name is required, adding no meaning beyond the schema; baseline 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?

'Create a sales opportunity' states a specific verb and resource, and the appended 'POST /Opportunities' pins the underlying operation. It is clearly distinct from siblings such as insightly_create_contact or insightly_create_lead by resource name, though it never explicitly contrasts itself with them or with insightly_update_opportunity.

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?

The description gives no when-to-use context, no preconditions, and no pointer to the alternative (insightly_update_opportunity) when the record already exists. The only guidance is the redundant note that opportunity_name is required.

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