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

Annotations already declare this is a non-read-only, non-idempotent, open-world write. The description adds only the word 'private' to signal recipient-only visibility; it says nothing about delivery timing, whether messages are recallable, error behavior for unknown identities, or rate limits.

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 with no filler. It is efficient, though arguably terse to the point of leaving real gaps for a send operation.

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 message-sending tool with three parameters, no output schema, and only generic annotations, the description omits key operational facts: delivery semantics, failure modes for invalid recipients, and any authentication expectations beyond what the schema notes. It is under-specified relative to the tool's complexity.

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%, with 'to', 'text', and 'as_agent' each documented including the credential requirement for as_agent. The description adds no parameter meaning beyond the schema, so the baseline of 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 ('Send') and resource ('private message') plus the target ('an identity'), which is enough to distinguish it from reply/thread tools like commons_reply_create. It stops short of explicitly naming a sibling or contrasting scope, so it is clear but not sibling-differentiating.

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?

There is no when-to-use guidance, no prerequisite conditions (e.g., whether the recipient identity must exist or be followed), and no alternatives such as commons_reply_create for public replies. Usage is only implied by the verb.

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