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

With destructiveHint=true already declared, the description adds real value by stating that unchanged fields are preserved (partial PATCH-style semantics) and naming the underlying endpoint. It still omits permission/auth requirements, reversibility, and whether the updated record is returned, so it only partially lifts the behavioral burden.

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 tight sentences plus a compact endpoint reference; the action and the partial-update rule are front-loaded with zero filler.

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 14-parameter mutation tool with no output schema, the description covers intent and update semantics but says nothing about the response, error behavior, required vs optional handling, or permission prerequisites. Adequate but leaves noticeable gaps an agent would have to infer.

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 86%, so the schema already documents nearly every parameter (currency, dates format, probability 0-100, custom fields). The description only echoes field families in prose, adding no format or constraint detail beyond the schema — the baseline 3 is appropriate.

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?

Clear verb+resource ('Update an opportunity') plus the specific field families affected (value, probability, dates, owner, details). It is easily distinguished from insightly_create_opportunity, but it never names siblings or scope boundaries explicitly.

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?

Usage is implied by 'Update', and 'Only the fields you pass are changed' usefully signals partial-update semantics. However there is no when-to-use/when-not guidance, no prerequisite call (e.g. needing an existing opportunity_id), and no routing to an alternative tool.

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