Follow announcement channel

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

Annotations already indicate this is a mutating (readOnlyHint=false) but not destructive operation. The description adds the behavioral effect of crossposted messages appearing in the target, which is useful context. However, it does not disclose potential side effects like duplicate subscriptions, permission requirements, or irreversibility, which would be valuable for a write operation.

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 a single, well-structured sentence. It front-loads the action and clearly states the purpose without any redundant words. Every word earns its place, making it highly concise and readable.

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?

The tool is simple and the description adequately explains the operation and its outcome. Given that there is no output schema, the description focuses on the effect rather than return values, which is appropriate. It could mention prerequisites like the source being an announcement channel, but this is implied by the parameter descriptions and the sibling tool context.

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%: all three parameters (guild, source, target) have clear descriptions in the input schema. The description does not add extra parameter-level detail beyond what the schema already provides, so the baseline score of 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 clearly states the action ('Subscribe a channel to an announcement channel') and the effect ('crossposted messages from the source appear in the target'). It uses a specific verb and resource, and this tool is distinct from siblings like crosspost_message or send_message, which handle one-off messages rather than persistent subscriptions.

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?

The description provides clear context for when to use this tool: when you want to set up automatic crossposting from an announcement channel to another channel. It does not explicitly mention alternatives or exclusion criteria, but the use case is unambiguous from the sibling toolset (e.g., crosspost_message is for individual posts, while this is for ongoing subscription).

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