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

Annotations already declare readOnly=false, idempotent=true, destructive=false and openWorld=false, so the safety profile is covered. The description nonetheless adds genuinely non-obvious impact context — 'nothing is sent to the prospect and no campaign step is affected' — which is exactly the kind of side-effect clarification an agent needs before writing. It stops short of saying what is returned after an upsert.

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 short sentences with zero filler. The create/update mechanism is front-loaded, the closing action follows, and the disambiguation against `reminder_create` sits last where it is least needed for the primary call.

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?

Covers purpose, mode selection, completion semantics, side-effect scope and an alternative — enough to call the tool correctly despite nine parameters. The one real gap is that with no output schema, the description never says whether the created task's id is returned, which an agent would want for a follow-up update.

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 100%, so the baseline is 3, and the description adds a bit more by framing `taskId` as the create-vs-update switch and `isCompleted: true` as the close action. Those restate schema descriptions but reinforce the semantics in the operative context where the agent will read them, earning a small bump over baseline.

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 pair and resource ('Create a to-do, or update one') and immediately explains the discriminator between the two modes (passing `taskId`). The final sentence explicitly names the sibling tool it is not (`reminder_create`), so an agent can route without opening either schema.

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?

Gives explicit when-to-use branches: omit `taskId` to create, pass it to update, set `isCompleted: true` to close. It also names the alternative for a timed personal nudge (`reminder_create`), which is the only plausible sibling confusion for a task tool.

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