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JavaScript
Remote

reddit_subreddits_default

Read-only

Browse Reddit's default front-page communities without a keyword. Returns subreddit names, titles, subscriber counts, and an after cursor for paging to the next page.

Instructions

Browse Reddit's default front-page set of subreddits, 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 the default communities; 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 and destructiveHint=false, so the safety profile is covered. The description adds value beyond that by disclosing the return shape (subreddits list with name, title, subscriber count, description, type, NSFW flag) and the presence of an `after` paging cursor — details not present in any structured field, since there is no output schema.

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 tight sentences, front-loaded with the browse scope, then return shape, then the disambiguating alternative. No filler and no repetition of the schema's pagination essay.

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?

With no output schema, the description carries the return-value burden and does so by enumerating the returned fields and the paging cursor. Combined with annotations covering safety and a schema that exhaustively documents both parameters, an agent has everything needed to call this 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 description coverage is 100% and the `after` field's schema text is unusually rich (cursor opacity, truncation semantics, listing_status handling), so the schema does the heavy lifting. The description only restates that an `after` cursor exists for paging, adding no syntax or format detail beyond the schema — the baseline 3 for fully documented parameters.

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 (Browse) and resource (Reddit's default front-page set of subreddits) with a clear scope qualifier ('default front-page set, no keyword needed'). It also names the sibling it is not — reddit_search_communities — so an agent can route between them 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?

Explicitly gives the selection rule against reddit_search_communities ('use reddit_search_communities instead to SEARCH communities by keyword'). It does not, however, distinguish this tool from the closely related reddit_subreddits_popular and reddit_subreddits_new siblings, which an agent could easily confuse.

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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