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Canvas LMS MCP – Local Edition

by Fireiscoolsolo
OverviewSchemaSourceRelated ServersDiscussionsAdmin
JavaScript
Local

Post Submission Comment

post_submission_comment
Destructive

Posts a comment on your own assignment submission, visible to your instructor, with optional file attachments. Requires a confirm=true flag to execute.

Instructions

Post a comment on your own submission for an assignment, optionally with files attached. Your instructor sees it. To attach a file, upload it first with upload_comment_attachment. [IRREVERSIBLE: call without confirm=true first to preview, then re-call with confirm=true.]

Input Schema

NameRequiredDescriptionDefault
commentYesComment text, visible to your instructor.
confirmNoMust be true to actually execute. Omit or set false to get a dry-run preview first.
file_idsNoOptional file IDs returned by upload_comment_attachment, to attach to this comment.
course_idYesCanvas course ID, a numeric string such as "12345". Get it from list_courses.
assignment_idYesAssignment ID (numeric string). Get it from list_assignments or list_upcoming_assignments.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed4 schema fields changedv1.0.2
    • changedInput schema / properties / assignment_id / description
      Previous value: -"Canvas ID (numeric string)"New value: +"Assignment ID (numeric string). Get it from list_assignments or list_upcoming_assignments."
    • addedInput schema / properties / comment / description
      Added value: +"Comment text, visible to your instructor."
    • changedInput schema / properties / course_id / description
      Previous value: -"Canvas course ID"New value: +"Canvas course ID, a numeric string such as \"12345\". Get it from list_courses."
    • addedInput schema / properties / file_ids
      Added value: +{
+  "description": "Optional file IDs returned by upload_comment_attachment, to attach to this comment.",
+  "items": {
+    "type": "string"
+  },
+  "type": "array"
+}
  2. First observedv1.0.1

TDQS

A4.4/5.0
Behavior5/5

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

Annotations already flag destructiveHint=true and idempotentHint=false, and the description adds genuinely new behavioral context: the action is IRREVERSIBLE, visibility is instructor-facing, and a mandatory two-step dry-run-then-confirm pattern must be followed. That is exactly the extra context the annotations cannot convey.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Four short sentences, front-loaded with the action and audience, then the attachment prerequisite, then the irreversible-confirm warning which is the highest-risk item an agent must not miss. No filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a mutation tool with no output schema, the description covers visibility, attachment prerequisite, and the confirm safety flow, and annotations cover the safety profile. It does not say whether the posted comment can later be edited or deleted, nor what a successful call returns, which leaves a small gap for an irreversible write.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% and all five parameters are documented in the schema, including confirm's dry-run semantics and file_ids' provenance from upload_comment_attachment. The description mostly restates those points rather than adding new parameter meaning, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Post a comment on your own submission for an assignment') with an explicit scope constraint ('your own submission') that separates it from discussion-posting siblings like post_entry or reply_to_entry. It also names the audience ('Your instructor sees it'), so the agent knows exactly what this call produces.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives concrete sequencing guidance: use upload_comment_attachment first when attaching files, and call without confirm=true first for a preview. It does not explicitly rule out alternatives or state prerequisites such as submission ownership/enrollment, so it stops short of a full when/when-not map.

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

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