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

Annotations already cover the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true), so the bar is lower, and the description still adds two things beyond them: that delivery happens via in-app notification or e-mail, and that the text should be reviewed with the user before sending. It stops short of saying whether the message is external-facing/irreversible or how the channel is chosen.

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 sentences, zero filler, with the action front-loaded and the confirmation requirement immediately after. Nothing could be trimmed without losing information.

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 simple two-parameter tool with no output schema, the description covers what the tool does and the key safety behavior. The one unresolved gap an agent would hit is how the in-app vs e-mail channel is determined, since no parameter exposes it and the description does not say.

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 coverage is 100%, so leadId ("Id from list_leads") and message (2000 char limit) are already fully documented. The description adds no meaning beyond the schema for either parameter, so the 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 and resource ("Sends a message to a lead") and scopes it to lead outreach, which separates it from the generic send_message and from read-only siblings like read_lead_chat. It does not explicitly name which sibling to prefer, so differentiation is implied rather than stated.

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 instruction "Show the text to the person before sending" is a genuine pre-send confirmation guideline, which is real usage guidance for a mutating tool. However, it gives no guidance on when to use this versus send_message or read_lead_chat, and no prerequisites (e.g. must the lead be in a specific state).

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