Replace the proprietary "args" front-matter key with an MCP-compliant "inputSchema" key

crates/runvil-internal/engine/src/execute/context-bound.rs

@@ -82,13 +82,13 @@ pub(super) fn bound_model_set(prompt: &Prompt, bindings: &ModelBindings) -> Mode
 }
 
 /// Derives a section's `argv` from the args string under the prompt's
-/// declaration: a default-declared prompt wraps the interface prose into
-/// the default shape (`argv.prose`, with the empty string present, not
-/// absent); a structured declaration parses the string as JSON, and a parse
+/// `inputSchema`: a prompt without one wraps the interface prose into
+/// `argv.prose` (with the empty string present, not absent); a prompt with
+/// one parses the string as JSON, and a parse
 /// failure or a JSON `null` reads as nil (`if argv then` is the malformed
 /// check). The executor never hard-errors on shape.
 pub(super) fn derive_argv(prompt: &Prompt, args: &str) -> Option<serde_json::Value> {
-    if prompt.frontmatter().args().is_default() {
+    if prompt.frontmatter().input_schema().is_none() {
         return Some(serde_json::json!({ "prose": args }));
     }
     match serde_json::from_str(args) {

crates/runvil-internal/engine/src/execute/tests/suite/args_surface.rs

@@ -1,17 +1,17 @@
 //! The args/argv surface: `args` is the exact passed string always; `argv`
 //! is the parsed JSON on success and nil otherwise (`if argv then` is the
-//! malformed check); a default-declared prompt wraps interface prose into
-//! `argv.prose`; `argv` is writable in H1 only and frozen when H1 completes,
+//! malformed check); a prompt without an `inputSchema` wraps interface
+//! prose into `argv.prose`; `argv` is writable in H1 only and frozen when H1 completes,
 //! so an H1 repair reaches every downstream section while an H2 assignment
 //! is an error; and `{{ argv }}` joins the prose substitution namespaces.
 
 use runvil_parser::test_support::{PromptSource, prompt};
 
 use crate::test_support::scenario::Scenario;
 
-/// One declared (required) `query` string. The declaration advertises and
+/// An input schema with one `query` string. The schema advertises and
 /// documents; it never enforces - enforcement is the prompt's H1.
-const QUERY: &str = "args: { query: { type: string } }";
+const QUERY: &str = "inputSchema: { type: object, properties: { query: { type: string } } }";
 
 /// A prompt declaring [`QUERY`] whose one section `Only` runs `lua`.
 fn query_prompt(lua: &str) -> String {
@@ -177,7 +177,7 @@ fn absent_is_not_the_empty_string() {
     // An optional field omitted is nil; passed empty it is "". The two are
     // distinguishable in Lua.
     let source = prompt(
-        "args: { prose: { type: string, optional: true } }",
+        "inputSchema: { type: object, properties: { prose: { type: string } } }",
         &[(
             "Only",
             "
@@ -193,8 +193,8 @@ fn absent_is_not_the_empty_string() {
 }
 
 #[test]
-fn a_default_declared_prompt_wraps_interface_prose() {
-    // No `args:` key: the default declaration wraps prose into argv.prose,
+fn a_prompt_without_an_input_schema_wraps_interface_prose() {
+    // No `inputSchema:` key: the input text wraps into argv.prose,
     // and args still holds the exact passed string.
     let source = prompt(
         "",
@@ -211,7 +211,7 @@ fn a_default_declared_prompt_wraps_interface_prose() {
 }
 
 #[test]
-fn a_default_declared_prompt_wraps_empty_prose_as_present() {
+fn a_prompt_without_an_input_schema_wraps_empty_prose_as_present() {
     // Interface prose is always present, so empty prose wraps as the
     // present empty string, distinguishable from an absent field.
     let source = prompt(

crates/runvil-internal/engine/src/execute/tests/suite/global_metatable.rs

@@ -10,7 +10,8 @@ use crate::test_support::scenario::Scenario;
 
 /// One declared `query` string, so `argv` is the parsed JSON or nil.
 fn query_source() -> PromptSource {
-    PromptSource::new().front("args: { query: { type: string } }")
+    PromptSource::new()
+        .front("inputSchema: { type: object, properties: { query: { type: string } } }")
 }
 
 #[test]

crates/runvil-internal/parser/Cargo.toml

@@ -12,6 +12,7 @@ runvil-lua.workspace = true
 runvil-types.workspace = true
 pulldown-cmark.workspace = true
 serde.workspace = true
+serde_json.workspace = true
 serde_yaml_ng.workspace = true
 thiserror.workspace = true
 

crates/runvil-internal/parser/src/contract.rs

@@ -1,16 +1,17 @@
-//! Parses the frontmatter contract keys: `uses`, `args`, and `models`.
+//! Parses the frontmatter contract keys: `uses`, `inputSchema`, and
+//! `models`.
 //!
-//! The YAML is the whole contract: Packs install, models declare, args
-//! type. Parsing validates the static shape - each `uses:` entry a bare
-//! Pack id or vendor/name, no Pack id declared twice, the alias grammar
-//! on map keys, the closed
-//! model-keyword vocabulary, arg name and type sanity - and exposes the
+//! The YAML is the whole contract: Packs install, models declare, the
+//! input schema types. Parsing validates the static shape - each `uses:`
+//! entry a bare Pack id or vendor/name, no Pack id declared twice, the
+//! alias grammar on model labels, the closed model-keyword vocabulary, the
+//! input schema's object shape - and exposes the
 //! FULL declaration on the parsed [`Prompt`](crate::Prompt); satisfying
 //! the declaration against the caller's environment is prepare's job,
 //! never the parser's.
 //!
-//! `args` and `models` are defined in submodules; this root owns the
-//! duplicate-Pack check and the map deserializer the two map keys share.
+//! `inputSchema` and `models` are defined in submodules; this root owns
+//! the duplicate-Pack check and the contract map deserializer.
 
 use std::collections::btree_map::Entry;
 use std::collections::{BTreeMap, BTreeSet};
@@ -21,19 +22,17 @@ use runvil_types::packs::{PackId, PackRef};
 use serde::de::{self, MapAccess, Visitor};
 use serde::{Deserialize, Deserializer};
 
-mod args;
+pub(crate) mod input_schema;
 mod models;
 
 #[cfg(test)]
 mod tests;
 
-pub use args::{ArgDecl, ArgType, ArgsDecl, ArgsDeclIter};
 pub use models::{ModelKeyword, ModelRole, ModelRoles, ModelRolesIter};
 
 /// The prompt-local alias grammar: `[A-Za-z][A-Za-z0-9_-]{0,63}`.
 ///
-/// Model labels and args field names are prompt-local and never global
-/// names. (The same rule sits in `runvil-lua`'s `alias` module, the
+/// Model labels are prompt-local and never global names. (The same rule sits in `runvil-lua`'s `alias` module, the
 /// run-time counterpart to this parse-time check.)
 fn is_valid_alias(alias: &str) -> bool {
     let bytes = alias.as_bytes();
@@ -51,7 +50,7 @@ struct ContractKeys {
     what: &'static str,
 }
 
-/// Deserializes a contract map (`models`, `args`): string keys
+/// Deserializes a contract map (`models`): string keys
 /// validated against the alias grammar and `keys`, values deserialized as
 /// `T`, duplicates rejected.
 fn deserialize_contract_map<'de, D, T>(