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

Adds meaningful context beyond the annotations: a 60-minute edit window, a default per-call confirmation that can be disabled, a warning to confirm with the user before each call because it reaches other people, and the required API key scope. Annotations only cover openWorldHint and non-destructive write; the description's confirmation and permission details are substantially useful. One minor gap: it does not clarify whether messages are plain text only or whether attachments are impossible.

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?

Front-loads the core action and scope, then moves through timing, confirmation, safety, and auth requirements in a logical order. Mostly tight, but it repeats 'Everfit' and 'message to a client' slightly (the bolded sentence duplicates the opening idea), which costs a point.

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 what the agent needs to know for safe invocation: who receives it, timing constraints, confirmation behavior, and auth. No output schema exists, but the description does not explain the return value (e.g., message ID or delivery confirmation); however, for a send tool with the rich behavioral context already present, this is a minor omission.

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 schema already documents both client_id and text completely. The description adds no syntax, formatting, or length constraints for the message text beyond what the schema provides, which is the baseline 3 for high-coverage schemas.

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?

Starts with a specific verb+resource ('Send a message to a client in Inbox') and immediately adds scope ('as you', 'one client in your Inbox conversation'). Distinguishes from the broadcast sibling everfit_send_broadcast by emphasizing one-to-one delivery.

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?

Implicitly establishes when to use this tool vs everfit_send_broadcast (one client vs many). Provides an important timing constraint ('edit only within 60 minutes') and confirms channels ('Inbox'), but does not explicitly name alternatives, so a 5 is not warranted.

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