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MCP Server

tabnas

dev.tabnas/mcp
Developer Tools Public & reachable MCP 2026-07-28

What this MCP does

Parses, validates, tests, diagnoses, and compares grammars using the tabnas parsing engine and plugins.

Capabilities

Tools

7 tools
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.
Input schema 
{'type': 'object', 'required': ['a', 'b'], 'properties': {'a': {'type': 'object', 'description': 'Baseline grammar: the serialized GrammarSpec already deployed.'}, 'b': {'type': 'object', 'description': 'Candidate grammar: the serialized GrammarSpec proposed to replace it.'}, 'depth': {'type': 'integer', 'maximum': 5, 'minimum': 0, 'description': 'Derivation depth for generated inputs (default 3).'}, 'corpus': {'type': 'array', 'items': {'type': 'string'}, 'description': 'Inputs to replay through both grammars, comparing acceptance and tree shape.'}, 'options': {'type': 'object', 'description': 'TabnasOptions applied to both instances.'}}, 'additionalProperties': False}
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.
Input schema 
{'type': 'object', 'required': ['name'], 'properties': {'name': {'type': 'string', 'description': 'Plugin name.'}}, 'additionalProperties': False}
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).
Input schema 
{'type': 'object', 'required': ['input'], 'properties': {'input': {'type': 'string', 'description': 'Source text to parse.'}, 'grammar': {'type': 'object', 'description': 'Serialized GrammarSpec (pure JSON, no functions). Schema: resource tabnas://schema/grammar. Grammars are validated before use; a `ref` key or a non-builtin function reference is rejected.'}}, 'additionalProperties': False}
list_plugins
List every bundled tabnas plugin descriptor (tabnas.plugin.json of each fleet repo), sorted by name. Returns {plugins:[...]}.
Input schema 
{'type': 'object', 'properties': {}, 'additionalProperties': False}
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.
Input schema 
{'type': 'object', 'required': ['input'], 'properties': {'input': {'type': 'string', 'description': 'Source text to parse.'}, 'grammar': {'type': 'object', 'description': 'Serialized GrammarSpec (pure JSON, no functions). Schema: resource tabnas://schema/grammar. Grammars are validated before use; a `ref` key or a non-builtin function reference is rejected.'}, 'options': {'type': 'object', 'description': 'TabnasOptions applied to the fresh instance before the grammar. Data only: a plugins entry is rejected.'}}, 'additionalProperties': False}
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.
Input schema 
{'type': 'object', 'required': ['spec'], 'properties': {'spec': {'type': 'string', 'description': 'TSV fixture content (not a path).'}, 'grammar': {'type': 'object', 'description': 'Serialized GrammarSpec (pure JSON, no functions). Schema: resource tabnas://schema/grammar. Grammars are validated before use; a `ref` key or a non-builtin function reference is rejected.'}, 'options': {'type': 'object', 'properties': {'inputCol': {'type': ['integer', 'string'], 'description': 'Input column, by position or header name. Default 0.'}, 'expectedCol': {'type': ['integer', 'string'], 'description': 'Expected column, by position or header name. Default 1.'}}, 'additionalProperties': False}}, 'additionalProperties': False}
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.
Input schema 
{'type': 'object', 'required': ['grammar'], 'properties': {'grammar': {'type': 'object', 'description': 'Serialized GrammarSpec (pure JSON, no functions). Schema: resource tabnas://schema/grammar. Grammars are validated before use; a `ref` key or a non-builtin function reference is rejected.'}}, 'additionalProperties': False}
History

Recent tool changes

Added
compare_grammars
Sept. 17, 2026, 12:39 p.m.
Added
describe_plugin
Sept. 17, 2026, 12:39 p.m.
Added
list_plugins
Sept. 17, 2026, 12:39 p.m.
Added
test_grammar
Sept. 17, 2026, 12:39 p.m.
Added
explain_parse_error
Sept. 17, 2026, 12:39 p.m.
Added
validate_grammar
Sept. 17, 2026, 12:39 p.m.
Added
parse
Sept. 17, 2026, 12:39 p.m.
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