Update Channel Message

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

Annotations indicate readOnlyHint=false (mutation), destructiveHint=false (not destructive), and idempotentHint=true (idempotent). The description mentions the sender restriction, which is a behavioral constraint not covered by annotations. However, it does not disclose other effects like whether formatting or mentions are replaced entirely, or if there are rate limits. Given that idempotentHint is true, the description could be more transparent about the idempotent behavior, but it adds some value beyond annotations.

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 concise, one sentence that clearly states the action and includes the sender restriction. It is appropriately front-loaded with the action and resource. The sentence has no fluff, though it could be slightly expanded to mention alternatives, but it is efficient and easy to parse.

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 has 9 parameters and no output schema, the description is somewhat minimal. It covers the essential who (sender) and what (update message), but does not explain return values, error conditions, or how the 'message' parameter interacts with other fields like 'format' or 'mentions'. For a mutation tool with moderate complexity, a bit more context would help, such as noting that the entire message content is replaced or that ID fields are required.

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%, so all 9 parameters are documented in the schema. The description itself does not add extra details about the parameters, but it does mention 'message' as the new content. With full schema coverage, the baseline is 3, and the description does not need to repeat parameter definitions. No additional semantics are provided beyond what the schema already offers.

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 updates (edits) a previously sent message in a channel, specifying the resource and action. It distinguishes from sibling tools like send_channel_message and delete_channel_message, but does not explicitly name alternatives. The phrase 'Update (edit) a message in a channel that was previously sent' is specific enough, though it could be more explicit about the distinction from updating chat messages.

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 the key context that only the sender can update their own messages, which is a critical usage constraint. However, it does not explicitly state when to use this tool versus alternatives such as reply_to_channel_message or update_chat_message. The sibling list includes similar tools for chat messages, so clearer routing would be beneficial, but the sender restriction is a concrete guideline.

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