messages_crosspost

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

Discloses the prerequisite (channel type 5) and the failure mode (400 error), plus the return fields. Annotations already indicate mutation (readOnlyHint=false), so description adds useful context beyond annotations without contradiction.

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?

The description is well-structured with clear sections (Purpose, When to use, When NOT to use, Returns) and is front-loaded. Every sentence is informative with no redundancy.

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?

Given the tool's simplicity, the description covers purpose, usage, failure conditions, and returns. It lacks explicit permission requirements, but the annotations and output schema compensate, making it sufficiently complete for tool selection.

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% with descriptions for all parameters. The description adds crucial semantics by specifying that the channel must be an Announcement channel and that the message is an existing announcement, reinforcing the schema's parameter meanings.

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 clearly states the tool publishes/crossposts a message from an Announcement channel to all following channels. The verb 'Publish (crosspost)' is specific and the resource is well-defined, distinguishing it from sibling tools like messages_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?

Provides explicit 'When to use' and 'When NOT to use' sections, including a clear alternative (messages_send) for fresh content and a specific error condition (non-Announcement channel). This fully guides the agent in tool selection.

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