Reply in Channel Thread

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

Annotations already indicate a non-read, non-destructive mutation. The description adds meaningful context: the reply will be 'org-visible to the channel' and it will 'return the posted reply', clarifying the side effect and expected output. It does not mention rate limits or auth, but annotations cover the safety profile.

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 two sentences, front-loaded with the purpose and side effect. The second sentence compactly delivers resolution guidance and required-parameter confirmation. No unnecessary words.

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 3 required params, no output schema, and existing annotations, the description is complete: it covers purpose, membership requirement, visibility, return value, prerequisite resolution, and confirms required params. It fully enables correct selection and invocation.

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 has 100% coverage with each parameter described, so baseline is 3. The description goes beyond schema by explicitly explaining that all three are required and providing resolution paths (channel_id via list_channels, parent_id via read_channel), which adds practical guidance.

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: 'Reply in a thread under a specific message in a Comms channel you belong to', which is specific and differentiates from siblings like post_to_channel (top-level posts) and reply_to_conversation. It also includes the resource scope ('as the connected member') and return value.

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 explicit guidance on resolving channel_id via list_channels and parent_id via read_channel, which are necessary prerequisites. It clearly implies the context of replying to a thread but does not explicitly name alternatives or exclusions, so it is not a full 5.

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