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

With no annotations, the description carries the full burden and discloses the read cursor advancement and the specific channel_not_found error for non-members. However, it omits other behaviors like rate limits, auth requirements, or success response format.

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 concise sentences: the first states the core purpose and side effect, the second gives error behavior. Every word earns its place, and key information is front-loaded.

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 the main action, side effect, and an important error case. While it doesn't describe the success return (no output schema) or broader context like rate limits, it is adequate for a post operation with complete schema documentation.

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 100%, and the description only repeats the channel name-or-id semantics already in the schema. It adds no new parameter details beyond what the schema provides, so baseline 3 is appropriate.

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 states a specific action (post) on a specific resource (channel by name or channel_id) and adds a distinctive side effect (advances read cursor). This clearly differentiates it from generic send tools like host.msg.send.

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?

No explicit mention of when to use this tool over siblings such as host.msg.send or host.channel.read. The member/non-member error behavior provides context but does not guide alternative selection.

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