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tabnas MCP Server

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answering

tabnas is answering right now. Last checked 8 min ago. 69 installs a week from npm. It exposes 7 tools. Last commit 8 Oct 2026.

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

Installs per day peak 200 · avg 18 · -42% w/w
a month agotoday
Uptime history 80 days of history · worst day 92%
80 days agonow
100.0%
Uptime 24h
91 of 91 checks
7
Tools
read from the server
138 ms
Response time
average over 24h
69
Installs / week
npm and PyPI

What changed 9

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

8 Oct a tool changed version
7 Oct a tool changed version
6 Oct a tool changed version
3 Oct a tool changed version
24 Sep a tool changed version
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

What the code does

We read the source, 9 h ago · tools taken from the live server · rules 995398eba69f

Capabilities

What this server is able to do. For an MCP server this is often the job itself — a terminal server runs commands because that is what it is for. Listed so you know what you are plugging in, not as an accusation.

File ships in the package but is absent from the source [пакет] src/grammar-validator.js:1, [пакет] src/data-bundle.ts:1 
этот файл ставится пользователю, но в репозитории его нет

Is this your server and something here is wrong? Tell us — corrections are free and do not require a plan.

This code can reach further than it looks

We found places where it runs commands, builds paths or queries from values it is given. None of that is a flaw by itself — it becomes one when the code changes, and code changes quietly between releases. We re-read it on every one.

Three servers free · no card

Connect this server

Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 8 min ago.

run in your terminal
claude mcp add mcp --transport http https://mcp.tabnas.dev/mcp
Settings → Connectors → Add custom connector, then paste this address
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
{
  "servers": {
    "mcp": {
      "type": "http",
      "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

URLTransportStateLatencyChecked
https://mcp.tabnas.dev/mcp streamable-http answering 94 ms 8 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 91 of 91 checks got a reply (100.0%), average response time 138 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 in the form 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 138 ms on average, which is faster than 85% 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 69 times in the last week. Week over week that is -42%. 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?
The code is open source: it is published under the MIT licence, written in JavaScript and 0 stars on GitHub. The licence covers the code in the repository, not the hosted service at mcp.tabnas.dev, which runs on its operator's own terms.