tabnas MCP Server

by tabnas Your server? Claim it

answering

tabnas is answering right now. Last checked 6 min ago. 53 installs a week from npm. It exposes 7 tools. Last commit 14 Sep 2026.

Seven tools over the tabnas parsing engine: parse, validate, diagnose, fixtures, compare.

Installs per day peak 239 · avg 31 · +16% w/w

a month agotoday

Uptime history 33 days of history · worst day 95%

33 days agonow

94.5%

Uptime 24h

86 of 91 checks

Tools

read from the server

118 ms

Response time

average over 24h

Installs / week

npm and PyPI

What changed 4

Every tool that appeared, vanished or quietly changed what it asks for. Recorded since 21 August 2026. No other catalogue keeps this.

22 Aug a tool changed version

21 Aug a tool changed version2 times that day

21 Aug a tool description was rewritten validate_grammar

and 1 more, back to 21 August 2026

tabnas does not always answer

Over the last week it answered 98.7% of our checks. We check every 15 minutes, so you hear about the next outage within the hour — not from your users.

Connect this server

Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 6 min ago.

Claude Code Claude Desktop Codex Cursor VS Code

run in your terminal

claude mcp add mcp --transport http https://mcp.tabnas.dev/mcp

~/Library/Application Support/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "mcp": {
      "url": "https://mcp.tabnas.dev/mcp"
    }
  }
}

~/.codex/config.toml

[mcp_servers.mcp]
url = "https://mcp.tabnas.dev/mcp"

.cursor/mcp.json

{
  "mcpServers": {
    "mcp": {
      "url": "https://mcp.tabnas.dev/mcp"
    }
  }
}

.vscode/mcp.json

{
  "mcpServers": {
    "mcp": {
      "url": "https://mcp.tabnas.dev/mcp"
    }
  }
}

Available tools 7

Read directly from the server with tools/list, grouped by what they act on. If a tool disappears, we record the date.

compare

compare_grammars

Grammar compatibility (AX plan Phase 5): does candidate grammar B still accept what baseline A accepted, and does it build the same tree for inputs both accept? Returns EVIDENCE AND CONFIDENCE, never a bare verdict: {normalForm, proven[], observed[], changes[], counterexamples[], confidence, why}. confidence:'low' with a stated reason is a successful run, not a failure — language inclusion is undecidable in general, so anything outside the decidable subset is reported not-proven rather than incompatible. Supply `corpus` (real inputs) for the tier that measures what your documents actually do.

describe

describe_plugin

The full descriptor for one plugin, by package name ('@tabnas/csv') or bare fleet name ('csv'). Unknown names get {ok:false, errors} naming the known plugins.

explain

explain_parse_error

Parse input and explain the failure. Returns {failed:false} when the input parses; otherwise {failed:true, diagnostic, registry} where registry is the error-code registry entry {code,message,hint} for the diagnostic code (resource tabnas://errors), or null for a code the bundled registry does not know (e.g. a plugin-declared code).

parse

parse

Parse input with the tabnas engine. Returns {ok:true, tree} or, on parse failure, {ok:false, diagnostic} — the structured diagnostic described by resource tabnas://schema/diagnostic. An invalid grammar is rejected as {ok:false, errors:[{path,message}]}. Without a grammar the bare engine is used, which defines no rules and produces an undefined tree for every input.

plugins

list_plugins

List every bundled tabnas plugin descriptor (tabnas.plugin.json of each fleet repo), sorted by name. Returns {plugins:[...]}.

test

test_grammar

Run TSV fixture content against a grammar in a fresh instance, using the fleet fixture convention (@tabnas/support): line 1 is a header, the input column is escape-decoded, the expected column is JSON or ERROR / ERROR:<code>. Returns {pass, fail, rows:[{row,input,expected,got,ok}]}. Refuses more than 10000 rows.

validate

validate_grammar

Validate a serialized GrammarSpec. Structural validation against the bundled grammar schema, an engine load in a fresh instance, and a check that every rule reference (`p`, `r`) names a rule the grammar actually defines — a dangling reference loads cleanly and then fails at parse time with `unknown_rule`. Returns {ok:true, v} (v = declared builtin config-schema version, absent means 1) or {ok:false, errors:[{path,message}]}. Security: a grammar carrying a `ref` key, or any function reference that is not a $-suffixed engine builtin, is rejected — validating a grammar never runs supplied code.

Endpoints

URL	Transport	State	Latency	Checked
https://mcp.tabnas.dev/mcp	streamable-http	answering	85 ms	6 min ago

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tabnas — questions

Answers built from our own checks of this server.

What can tabnas do?

It exposes 7 tools, read directly from the server on our last check. Among them: compare_grammars, describe_plugin, explain_parse_error, list_plugins, parse, test_grammar and 1 more. The full list with descriptions is on this page — we take it from the server itself via tools/list, not from a README. How MCP servers expose tools in the first place →

Is tabnas working right now?

We send a real MCP handshake every 15 minutes. Over the last 24 hours 86 of 91 checks got a reply (94.5%), average response time 118 ms. The bar chart above shows every period we have measured.

How do I connect tabnas?

Copy the ready config from this page — we generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each with the file path that client actually reads. It is a remote server, so there is nothing to install — the client connects to the address.

Does tabnas need an API key?

No. tabnas completed a full MCP handshake with us as an anonymous client and listed its tools without asking for anything. All 7 of them are readable on this page. This is what we observed, not what the docs claim.

How fast is tabnas?

It answers our handshake in 118 ms on average, which is faster than 83% of all working MCP servers we measure. That puts it in the quick quarter of the ecosystem. The comparison comes from our own checks across the whole registry, every 15 minutes.

How many people use tabnas?

The npm package @tabnas/mcp was installed 53 times in the last week. Week over week that is +16%. We show installs rather than GitHub stars on purpose: a star is a bookmark, an install is someone actually running it.

Is tabnas open source?

Yes — it is published under the MIT licence, written in JavaScript, 0 stars on GitHub and 1 open issue. The source link is on this page, so you can read exactly what it does with your data before you connect it.