Reddit MCP Server

edit_post

DestructiveIdempotent

Overwrite the body text of your own self-text Reddit post. Provide the post ID and new markdown text; the previous body is replaced, marking the post as edited.

Instructions

Replace the body text of one of your own self-text posts. Mutating and idempotent (same text → same result); it overwrites the previous body. Requires REDDIT_USERNAME and REDDIT_PASSWORD, and works only on self posts you authored — titles and link posts cannot be edited. Adds an "edited" marker. Use create_post to make a new post, or edit_comment for comments. WARNING: rapid edits may trigger spam detection; enable REDDIT_SAFE_MODE for protection.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "thing_id": "<thing_id>",
      "new_text": "<new_text>"
    },
    "name": "edit_post"
  }
}

Input Schema

Name	Required	Description	Default
`new_text`	Yes	Replacement body text; fully overwrites the current body. Reddit markdown supported.
`thing_id`	Yes	The post to edit: a full thing id 't3_<id>' or just the base36 post id '<id>' (the 't3_' prefix is added automatically). Must be a self-text post you authored.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.5.3Aug 20, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Annotations provide idempotentHint, destructiveHint, and readOnlyHint=false. The description adds meaning beyond these: it states the overwrite behavior explicitly, mentions the 'edited' marker, requires REDDIT_USERNAME/PASSWORD credentials, and warns about spam detection. No contradiction with annotations; rather, it enriches them with operational context.

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?

The description is two sentences but packs: purpose, mutability, idempotency, credential requirements, scope, marker side-effect, alternative tools, and a safety warning. Every clause earns its place; no fluff. Information density is high while remaining readable.

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

Completeness5/5

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

For a mutating tool with no output schema, the description covers all essential operational aspects: what it does, prerequisites (credentials), constraints (self posts only), side effects (overwrite, marker), and risk (spam detection). The absence of output schema is acceptable since mutation result is straightforward. Complete guidance for an agent to invoke correctly.

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 coverage is 100% with detailed descriptions for both parameters (new_text explains overwrite and markdown support; thing_id explains format and ownership constraint). The description adds little beyond the schema—it reiterates overwrite and self-post constraint but introduces no new per-parameter semantics. Baseline 3 is appropriate given the schema's thoroughness.

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?

The description opens with a specific verb+resource: 'Replace the body text of one of your own self-text posts.' It clearly scopes to self-text posts, distinguishes from edit_comment and create_post, and clarifies that titles and link posts cannot be edited. This is fully differentiated from siblings.

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

Usage Guidelines5/5

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

Explicitly names alternatives: 'Use create_post to make a new post, or edit_comment for comments.' Also states conditions for use (self posts only, authored by you) and warns about rapid edits triggering spam detection, with a mitigation (REDDIT_SAFE_MODE). This gives clear when/when-not/alternatives guidance.

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