MCP Reddit Server

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reddit_topic

Get posts from multiple subreddits related to a given topic. Enter a topic to aggregate relevant Reddit discussions without manually browsing individual subreddits.

Instructions

Get posts from topic-related subreddits.

Args: topic: Topic name (e.g. programming) limit: Posts to fetch (default: 50) max_subreddits: Max subreddits (default: 20)

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": {
      "topic": "<topic>"
    },
    "name": "reddit_topic"
  }
}

Input Schema

Name	Required	Description	Default
`limit`	No
`topic`	Yes
`max_subreddits`	No

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Sep 6, 2026

TDQS

B3.4/5.0

Behavior2/5

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

With no annotations, the description carries the full burden of behavioral disclosure. It only states that posts are fetched from topic-related subreddits, but does not explain how subreddits are selected, how results are ordered, whether authentication is needed, or how limits are applied. These are significant gaps for a no-annotation tool.

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 concise and front-loaded: a one-sentence purpose statement followed by a compact parameter list. Every element earns its place and there is no redundant filler.

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

Completeness3/5

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

The output schema exists, so return values do not need elaboration, and all parameters are documented. However, the description is still incomplete for a tool without annotations because it omits behavioral details and any guidance on choosing this tool over its siblings, leaving the agent to guess when 'topic' semantics apply.

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

Parameters4/5

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

The schema has 0% description coverage, so the description must compensate, and it does by listing all three parameters with brief semantics: 'topic' as a name, 'limit' as posts to fetch, and 'max_subreddits' as a maximum. This adds meaningful context beyond the raw schema, though it could clarify bounds or example values further.

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

Purpose4/5

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

The description starts with a specific verb and resource: 'Get posts from topic-related subreddits.' This clearly indicates the tool's function and differentiates it from single-subreddit or front-page tools, though it does not explicitly name sibling tools.

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

Usage Guidelines3/5

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

The use case is implied by the tool's name and the 'topic' argument, suggesting it should be used when the user wants posts across subreddits related to a topic. However, there is no explicit guidance about when to prefer this over siblings like reddit_hot, reddit_top, or reddit_front, and no exclusions or alternative routing is provided.

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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