reply_to_discussion_entryPosts a reply to a student's discussion entry in Canvas, enabling feedback and continued conversation.
Reply to a student's discussion entry/comment.
| Name | Required | Description | Default |
|---|---|---|---|
| message | Yes | Reply message content | |
| entry_id | Yes | Discussion entry ID to reply to | |
| topic_id | Yes | Discussion topic ID | |
| course_identifier | Yes | Course code or Canvas ID |
Changes observed during successful MCP inspections.
v1.10.0Output schema / (root)Previous value: -{
- "properties": {
- "result": {
- "type": "string"
- }
- },
- "required": [
- "result"
- ],
- "type": "object",
- "x-fastmcp-wrap-result": true
-}New value: +nullv1.8.0Input schema / additionalPropertiesAdded value: +falseInput schema / properties / course_identifier / descriptionAdded value: +"Course code or Canvas ID"Input schema / properties / course_identifier / titleRemoved value: -"Course Identifier"Input schema / properties / entry_id / descriptionAdded value: +"Discussion entry ID to reply to"Input schema / properties / entry_id / titleRemoved value: -"Entry Id"Input schema / properties / message / descriptionAdded value: +"Reply message content"Input schema / properties / message / titleRemoved value: -"Message"Input schema / properties / topic_id / descriptionAdded value: +"Discussion topic ID"Input schema / properties / topic_id / titleRemoved value: -"Topic Id"Input schema / titleRemoved value: -"reply_to_discussion_entryArguments"Output schema / properties / result / titleRemoved value: -"Result"Output schema / titleRemoved value: -"reply_to_discussion_entryOutput"Output schema / x-fastmcp-wrap-resultAdded value: +truev1.0.0Input schema / titleAdded value: +"reply_to_discussion_entryArguments"Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare idempotentHint=false and destructiveHint=false, so the safety profile is partly covered. Beyond that, the description adds nothing: it doesn't say whether posting notifies the student/class, whether the instructor must be enrolled or subscribed, what happens if the topic is locked, or what is returned after the write. For a mutation tool this leaves meaningful behavior undisclosed.
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?
One short, front-loaded sentence with no filler. The 'entry/comment' hedge is slightly ambiguous vocabulary but costs little, and the sentence is appropriately sized for a four-parameter write tool.
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?
An agent has enough to construct a call correctly (all params documented, fully required). It is not complete for a mutation tool with no output schema, since the return value and side effects (notification, subscription, visibility) are never described.
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% and each of the four required parameters is documented in-schema, so the baseline of 3 applies. The description contributes no additional semantics — e.g., that entry_id must belong to the given topic_id, or what format course_identifier accepts beyond what the schema says.
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?
States a specific verb and resource: 'Reply to a ... discussion entry/comment,' so the agent knows exactly what action is performed. It does not, however, distinguish itself from the sibling post_discussion_entry, which also creates content in a discussion — the reply-vs-top-level distinction is left implicit.
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?
Usage is only implied by the required entry_id (you must have an existing entry to reply to). No explicit guidance contrasts this with post_discussion_entry or create_discussion_topic, and no prerequisites (enrollment, discussion permissions, whether the topic must be open) are stated.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.