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OverviewSchemaSourceRelated ServersDiscussionsAdmin
JavaScript
Remote

reddit_subreddits_popular

Read-only

Browse popular and trending subreddits without a keyword to discover communities by subscriber count. Returns names, titles, subscriber totals, descriptions, type, and an after cursor for paging.

Instructions

Browse the most-subscribed, trending subreddits right now, no keyword needed. Returns a subreddits list (each with name, title, subscriber count, description, type, and NSFW flag) plus an after cursor for paging. This BROWSES communities by popularity; use reddit_search_communities instead to SEARCH communities by keyword.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
afterNoOpaque pagination cursor. Pass back the previous response's `after` value EXACTLY as it was returned; the format is not stable and a hand-written Reddit fullname loses the paging depth the cursor carries. Omit on the first call. When `after` comes back null there is no next page to request, and that does NOT reliably mean you have every item: Reddit often stops serving a busy listing long before it runs out. Read `listing_status` on that final response instead. It is `complete`, `truncated` or `unknown`, and ONLY `complete` means nothing is missing. Never report `truncated` or `unknown` to a user as the end of the data; say the answer is partial and widen across sorts, timeframes or search terms.
limitNoMax items to return (1 to 100). The API clamps out-of-range values; endpoint default applies if omitted.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv0.5.3
    • changedInput schema / properties / after / description
      Previous value: -"Opaque Reddit pagination cursor from the previous response's `after` field (a fullname like `t3_abc123`). Omit on the first call; pass it to fetch the next page."New value: +"Opaque pagination cursor. Pass back the previous response's `after` value EXACTLY as it was returned; the format is not stable and a hand-written Reddit fullname loses the paging depth the cursor carries. Omit on the first call. When `after` comes back null there is no next page to request, and that does NOT reliably mean you have every item: Reddit often stops serving a busy listing long before it runs out. Read `listing_status` on that final response instead. It is `complete`, `truncated` or `unknown`, and ONLY `complete` means nothing is missing. Never report `truncated` or `unknown` to a user as the end of the data; say the answer is partial and widen across sorts, timeframes or search terms."
  2. First observedv0.1.12

TDQS

A4.3/5.0
Behavior4/5

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

Annotations already declare readOnlyHint=true, openWorldHint=true, destructiveHint=false, so the safety profile is covered. The description adds genuine context beyond that: it names the returned fields and the `after` cursor for paging. It omits the partial-data/listing_status caveat that the schema carries, so it is strong but not exhaustive.

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?

Three compact sentences, front-loaded with purpose and scope, then return shape, then the disambiguation instruction. No filler and nothing redundant with the schema.

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?

Read-only browse tool with zero required params, full schema coverage, and no output schema — so the description's own summary of the return payload and paging cursor fills the remaining gap. Nothing an agent needs to call it correctly is missing.

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%, so the schema already explains `after` (including the cursor-stability warning and listing_status semantics) and `limit` thoroughly. The description only echoes "an `after` cursor for paging" and adds no format or usage detail beyond it — baseline 3 is correct when the schema does all the work.

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?

Specific verb+resource ("Browse the most-subscribed, trending subreddits"), plus the scope qualifier "no keyword needed" and an explicit contrast with reddit_search_communities. An agent can distinguish this popularity-browse tool from the keyword-search sibling without opening either schema.

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?

States the selection condition clearly: use this to browse by popularity, use reddit_search_communities to search by keyword. It does not, however, distinguish itself from the other listing siblings (reddit_subreddits_new, reddit_subreddits_default, reddit_subreddit_top), which an agent choosing among browse endpoints would also need.

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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