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

Annotations already declare the write/non-destructive/non-idempotent profile, but the description adds real behavioral context: the note is agent-only and never delivered to the customer, plus the concrete endpoints used. It omits idempotency/reversibility detail, which the annotations partially cover.

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?

A single front-loaded sentence led by the 'WRITE:' tag; the visibility constraint and targeting options are packed in with no filler, and every clause earns its place.

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 write tool with no output schema, the description plus annotations and full-coverage schema give an agent enough to call it correctly: purpose, visibility semantics, and both targeting paths. It could be stronger with an explicit note about the resolve flag's side effect, but nothing essential is missing.

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 all five parameters are already documented, including the 'pass this OR' targeting and the open-on-missing behavior. The description restates the uuid/phone_number targeting without adding format or constraint detail beyond the schema, so 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?

States a specific verb (add) and resource (internal whisper/note) scoped to a conversation, and the parenthetical 'never sent to the customer' implicitly distinguishes it from textline_send_message. It stops short of naming the sibling explicitly, so it's clear but not fully differentiated.

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 visibility distinction ('note only your agents see, never sent to the customer') implies when to prefer this over send_message, and it explains the two targeting modes. However, there is no explicit when/when-not statement or named alternative, leaving the routing to inference.

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