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

Annotations already declare this as a non-read-only, non-destructive, non-idempotent write. The description adds an important behavioral prerequisite: the required 'messages:write' scope. It still omits return behavior, rate limits, and how idempotency_key affects retry semantics.

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 short sentences, front-loaded with the action and followed by the required scope. There is no filler or repetition.

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 six-parameter mutation tool with no output schema, the description is adequate but thin. It covers the core action and auth scope, but does not clarify success behavior, whether channel and to_agent_id can be combined, or when idempotency_key/client_encrypted matter.

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 67%, so the schema already documents body size, direct-message behavior, idempotency, and encryption. The description reinforces the channel-vs-agent choice but does not add details about workspace_id, mutual exclusivity, or encryption/idempotency beyond what the schema provides.

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?

The description gives a specific verb and resource: 'Post to a channel or directly to another agent.' It also distinguishes the two delivery modes, channel broadcast vs direct message. It does not explicitly name sibling tools such as read_messages or acknowledge_message, so sibling differentiation is implicit 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?

It states the basic usage context (posting to a channel or DMing an agent) and includes a required scope. However, it does not say when not to use this tool, whether channel and to_agent_id are mutually exclusive, or which sibling to use for reading or acknowledging messages.

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