Tool reference

This page is generated from the server's tool definitions (src/mcp/tool_meta.ts) — the same source the running server registers, so it never drifts.

All 9 tools are read-only (readOnlyHint: true), deterministic over the pinned spec commit, and perform no execution or network I/O.

spec_version

Return self-description of this MCP server: package name + version, plus the pinned upstream commit SHA for every spec snapshot baked into the package. Use this first when citing the spec, or to verify the server's freshness and reproducibility.

Title: Pinned spec version

No parameters.

instruction_get

Fetch one WebAssembly instruction by mnemonic (i32.add, br_if) or binary opcode (0x6a, 0xfd 0x89 0x02) as structured JSON: opcode bytes, category, introducing version, stack type signature, and validation/execution prose anchors + spec URLs. Provide mnemonic or opcode (mnemonic wins if both match).

Title: Get instruction

Field	Type	Required	Description
mnemonic	string	no	Instruction mnemonic, e.g. i32.add, br_if, local.get. Case-insensitive. Exact match.
opcode	string	no	Binary opcode as hex bytes, e.g. 0x6a, 6a, or multi-byte 0xfd 0x89 0x02. Exact match. Used when mnemonic is absent or doesn't match.
version	main | latest	no	WebAssembly spec version to query. latest (default) is the current served version; main is the upstream working draft. (default: latest)

Examples

• Get the i32.add instruction

  {"mnemonic":"i32.add"}

  Returns opcode 0x6a, the [i32 i32] → [i32] signature, and validation/execution anchors.
• What instruction is opcode 0x0d?

  {"opcode":"0x0d"}

  Reverse lookup by binary opcode — resolves to br_if.

instruction_list

Enumerate WebAssembly instructions with optional filters: category (control, numeric, parametric, variable, table, memory, ref, i31, struct, array, extern, vec), introduced_in (1.0 | 2.0 | 3.0), and prefix (mnemonic prefix like i32.). Returns lightweight rows sorted by opcode; follow up with instruction_get for full detail.

Title: List instructions

Field	Type	Required	Description
category	control | numeric | parametric | variable | table | memory | ref | i31 | struct | array | extern | vec	no	Filter by instruction category: control, numeric, parametric, variable, table, memory, ref, i31, struct, array, extern, vec (vector/SIMD).
introduced_in	1.0 | 2.0 | 3.0	no	Filter to instructions introduced in this WebAssembly version: 1.0, 2.0, or 3.0.
prefix	string	no	Filter to mnemonics starting with this prefix, e.g. i32. or v128.. Case-insensitive.
version	main | latest	no	WebAssembly spec version to query. latest (default) is the current served version; main is the upstream working draft. (default: latest)

Examples

• List all control-flow instructions

  {"category":"control"}

  Filters to the control category; rows are sorted by opcode.
• What memory instructions did Wasm 3.0 add?

  {"category":"memory","introduced_in":"3.0"}

  Combine category + introduced_in to see what a release contributed.
• List the i32 numeric instructions

  {"prefix":"i32."}

  Prefix filter is the quickest way to scope to one type family.

instruction_search

Search WebAssembly instructions by free-text query, matched against mnemonic (exact > substring), category name, and opcode hex. The entry point when you don't know the exact mnemonic. Returns ranked lightweight hits with a matched_on field; follow up with instruction_get.

Title: Search instructions

Field	Type	Required	Description
query	string	yes	Search text. Matched against mnemonic (exact > substring), category name, and opcode hex. E.g. extend, trunc, vec, 0x6a.
limit	number	no	Max ranked hits returned. (default: 20)
version	main | latest	no	WebAssembly spec version to query. latest (default) is the current served version; main is the upstream working draft. (default: latest)

Examples

• Find all the extend instructions

  {"query":"extend"}

  Substring match across mnemonics surfaces i32.extend8_s, i64.extend_i32_u, etc.
• Which instruction has opcode 0x6a?

  {"query":"0x6a"}

  A hex query also matches by opcode — resolves i32.add at the top.

type_get

Look up a WebAssembly type or type form by name: concrete value types (i32, i64, f32, f64, v128, funcref, externref, …) or type forms (functype, limits, memtype, tabletype, globaltype, reftype, valtype, rectype, heaptype, …). Returns its classification, sibling members for category types, defining clause prose, SpecTec formal-rule references, and the rendered spec URL.

Title: Get type

Field	Type	Required	Description
name	string	yes	Type or type-form name. Concrete value types: i32, i64, f32, f64, v128, funcref, externref, … Type forms: functype, limits, memtype, tabletype, globaltype, reftype, valtype, rectype, heaptype, … Case-insensitive, exact match.
version	main | latest	no	WebAssembly spec version to query. latest (default) is the current served version; main is the upstream working draft. (default: latest)

Examples

• What is the i32 type?

  {"name":"i32"}

  Returns kind=number, the sibling number types (i64/f32/f64), and the Number Types clause prose + URL.
• Describe a function type

  {"name":"functype"}

  Type forms like functype/limits/memtype resolve to their defining clause in the types section.

section_get

Fetch one spec clause by id or anchor, across core / js-api / web-api (set spec). For core: syntax-numtype, valid-unreachable, binary-instr, … For the embedding specs: modules, memories, streaming-modules, … Matches the rendered spec's stable fragment ids. Returns the clause title, cleaned prose, cross-references, the SpecTec formal_refs it cites (core), and the rendered URL. Core validation/execution clauses are SpecTec-generated: prose may be terse, but formal_refs + url point to the formal rule.

Title: Get spec section

Field	Type	Required	Description
id	string	yes	Clause id or anchor. For core: syntax-numtype, valid-unreachable, binary-instr, … For js-api / web-api: modules, memories, streaming-modules, … These match the stable fragment ids in the rendered spec.
spec	core | js-api | web-api	no	Which WebAssembly spec to query: core (default; instructions, types, validation, execution, formats), js-api (JavaScript embedding), or web-api (Web platform integration). (default: core)
version	main | latest	no	WebAssembly spec version to query. latest (default) is the current served version; main is the upstream working draft. (default: latest)

Examples

• Get the number types section

  {"id":"syntax-numtype"}

  Returns the Number Types clause: prose, the i32/i64/f32/f64 formal refs, and the spec URL.
• Read the validation rule anchor for unreachable

  {"id":"valid-unreachable"}

  Validation/execution clauses are SpecTec-spliced; prose may be terse but formal_refs names the rule and url links the rendered notation.

section_list

Enumerate spec clauses for navigation, across core / js-api / web-api (set spec). Filter by source path (core: intro, syntax, valid, exec, binary, text, appendix, or sub-paths like syntax/types), anchor_prefix, titled_only, and max_level. Returns lightweight rows {id, anchors, title, level, path, url}; follow up with section_get.

Title: List spec sections

Field	Type	Required	Description
spec	core | js-api | web-api	no	Which WebAssembly spec to query: core (default; instructions, types, validation, execution, formats), js-api (JavaScript embedding), or web-api (Web platform integration). (default: core)
path	string	no	Filter to a source path / prefix. Top-level areas: intro, syntax (structure), valid (validation), exec (execution), binary, text, appendix. Sub-paths like syntax/types also work.
anchor_prefix	string	no	Filter to clauses whose id/anchor starts with this prefix, e.g. syntax-, valid-, exec-.
titled_only	boolean	no	Drop anchor-only content blocks (keep only clauses with a heading). (default: false)
max_level	number	no	Cap heading depth (1 = page titles only). Anchor-only blocks are unaffected.
version	main | latest	no	WebAssembly spec version to query. latest (default) is the current served version; main is the upstream working draft. (default: latest)

Examples

• Outline the binary format sections

  {"path":"binary","titled_only":true}

  Path filter scopes to one area; titled_only yields a clean outline.
• List every validation clause

  {"anchor_prefix":"valid-"}

  Anchor-prefix filter gathers all clauses in one rule family.

spec_search

Full-text search across the section index of a spec (core / js-api / web-api, set spec) — clause anchors/ids, titles, and prose. The entry point when you don't know the exact anchor. Returns ranked hits with a matched_on field (anchor-exact > title > anchor > prose) and a prose snippet for body matches; follow up with section_get.

Title: Search spec

Field	Type	Required	Description
query	string	yes	Search text. Matched against clause anchors/ids, titles, and prose. E.g. block type, trap, funcref, streaming compilation.
spec	core | js-api | web-api	no	Which WebAssembly spec to query: core (default; instructions, types, validation, execution, formats), js-api (JavaScript embedding), or web-api (Web platform integration). (default: core)
limit	number	no	Max ranked hits returned. (default: 20)
version	main | latest	no	WebAssembly spec version to query. latest (default) is the current served version; main is the upstream working draft. (default: latest)

Examples

• Where does the spec define traps?

  {"query":"trap"}

  Ranks title matches above prose matches; prose hits include a snippet around the match.
• Find the block type section

  {"query":"block type"}

  Title substring search surfaces syntax-blocktype near the top.

proposal_list

List WebAssembly proposals and their phases from the pinned WebAssembly/proposals repository. Filter by status (phase-0…phase-5, finished, inactive), phase (0–5), champion substring, affects (finished proposals touching core / js-api / web-api), or contains (name/champion substring). Each row carries name, status, phase, champion, affected_specs, spec_version, and the proposal URL.

Title: List WebAssembly proposals

Field	Type	Required	Description
status	phase-0 | phase-1 | phase-2 | phase-3 | phase-4 | phase-5 | finished | inactive	no	Filter by lifecycle status: phase-0…phase-5, finished (merged into the spec), or inactive.
phase	number	no	Filter by numeric phase 0–5 (active + finished proposals carry a phase).
champion	string	no	Champion substring, case-insensitive.
affects	string	no	Filter to finished proposals affecting a given spec: core, js-api, or web-api.
contains	string	no	Name or champion substring, case-insensitive.

Examples

• What proposals are finished and in Wasm 3.0?

  {"status":"finished","affects":"core"}

  Finished proposals carry affected_specs + spec_version; filter by the spec they touched.
• What's in phase 3?

  {"phase":3}

  Phase filter scopes to one stage of the proposal process.