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

Annotations only give a generic non-read-only, non-destructive profile; the description goes well beyond by disclosing rate limits (5/hour per network), quota accounting when api_key is supplied, and the fact that every message is moderated before display. It stops short of saying what happens on moderation rejection or delivery latency, which keeps it from a 5.

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 tight sentences, no filler, with the routing rule front-loaded and the quota/moderation caveats following. Every sentence carries decision-relevant 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 5-parameter write-style tool with no output schema, it covers audience routing, auth semantics, rate limits, and the moderation gate. Missing details are outcome-related (what the caller receives, what happens if moderated out), which is a minor gap given no output schema exists.

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 60%, and the description meaningfully explains the two most ambiguous parameters: `to` (request id vs "operator") and `api_key` (quota-bearing optional auth). `contact`, `from_name`, and `body` are left to name inference and schema limits, a modest but real gap.

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+resource ('leave a message') and disambiguates the two target audiences directly: a request publisher via request id, or the site operator via the literal "operator". An agent can tell exactly what this does and to whom, and no sibling tool overlaps with it.

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 clear context for the two routing modes and the authenticated-vs-anonymous trade-off (api_key counts against daily quota; without it you are anonymous and capped at 5/hour per network). It doesn't name an alternative tool for other communication needs, but no sibling tool competes for this action.

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