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

Annotations already declare readOnlyHint=false, idempotentHint=false, openWorldHint=true, and destructiveHint=false, so the mutation and non-idempotent nature are known from structured data. The description adds valuable timing semantics ('Sending happens on this request'), clarifying that the send is immediate rather than queued, which is not inferable from annotations. It does not discuss error/failure outcomes or delivery semantics beyond immediate dispatch.

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, front-loaded with the primary action and target, then prerequisites and timing. No filler or repetition; each sentence serves a distinct purpose.

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 mutation tool with annotations covering safety profile and no output schema, the description covers the core action, target, plan requirement, and immediate-send behavior. It stops short of failure modes, delivery outcomes, or channel selection guidance. Adequate but with clear gaps for an agent deciding whether and how to call it.

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%; all three parameters are described in the schema. The description adds no parameter-level detail (e.g., format of phone number, Widely channel selection, identity_id usage). Baseline 3 applies when the schema carries parameter semantics.

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 (sends) and resource (SMS or Widely message) with immediate channel targets (phone number or saved contact). Clearly distinguishable from read-oriented siblings like search_messages and get_thread.

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?

Mentions 'Pro plan' as a prerequisite, which is useful context. However, there is no explicit when-to-use guidance versus alternatives (e.g., when SMS vs Widely channel is chosen, or relation to request_speak/request_call). Usage is implied but not framed.

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