lash_sansio/
tool_contract.rs

1use crate::{SchemaContract, SchemaProjectionOverride};
2
3/// Automatic retry policy for a tool's execution.
4///
5#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
6#[serde(tag = "type", rename_all = "snake_case")]
7pub enum ToolRetryPolicy {
8    /// Never retry automatically. This is the default for every tool.
9    #[default]
10    Never,
11    /// Retry only failures that explicitly report a safe retry disposition.
12    Safe {
13        max_attempts: u32,
14        base_delay_ms: u64,
15        max_delay_ms: u64,
16    },
17    /// Retry only failures that explicitly report a safe retry disposition,
18    /// and only when the runtime can provide a stable replay key.
19    Idempotent {
20        max_attempts: u32,
21        base_delay_ms: u64,
22        max_delay_ms: u64,
23    },
24}
25
26impl ToolRetryPolicy {
27    pub fn safe(max_attempts: u32, base_delay_ms: u64, max_delay_ms: u64) -> Self {
28        Self::Safe {
29            max_attempts,
30            base_delay_ms,
31            max_delay_ms,
32        }
33    }
34
35    pub fn idempotent(max_attempts: u32, base_delay_ms: u64, max_delay_ms: u64) -> Self {
36        Self::Idempotent {
37            max_attempts,
38            base_delay_ms,
39            max_delay_ms,
40        }
41    }
42
43    pub fn max_attempts(self) -> u32 {
44        match self {
45            Self::Never => 1,
46            Self::Safe { max_attempts, .. } | Self::Idempotent { max_attempts, .. } => {
47                max_attempts.max(1)
48            }
49        }
50    }
51
52    pub fn delay_ms_for_retry(self, retry_index: u32, requested_after_ms: Option<u64>) -> u64 {
53        let (base_delay_ms, max_delay_ms) = match self {
54            Self::Never => return 0,
55            Self::Safe {
56                base_delay_ms,
57                max_delay_ms,
58                ..
59            }
60            | Self::Idempotent {
61                base_delay_ms,
62                max_delay_ms,
63                ..
64            } => (base_delay_ms, max_delay_ms),
65        };
66        let multiplier = 1_u64.checked_shl(retry_index).unwrap_or(u64::MAX);
67        let backoff = base_delay_ms.saturating_mul(multiplier);
68        let delay = requested_after_ms.unwrap_or(backoff);
69        if max_delay_ms == 0 {
70            delay
71        } else {
72            delay.min(max_delay_ms)
73        }
74    }
75
76    pub fn requires_replay_key(self) -> bool {
77        matches!(self, Self::Idempotent { .. })
78    }
79}
80
81fn default_tool_retry_policy() -> ToolRetryPolicy {
82    ToolRetryPolicy::default()
83}
84
85fn is_default_tool_retry_policy(policy: &ToolRetryPolicy) -> bool {
86    *policy == ToolRetryPolicy::default()
87}
88
89#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
90#[serde(rename_all = "snake_case")]
91pub enum ToolActivation {
92    #[default]
93    Always,
94    Internal,
95}
96
97fn is_default_tool_activation(activation: &ToolActivation) -> bool {
98    *activation == ToolActivation::default()
99}
100
101#[derive(Clone, Debug, Default, PartialEq, serde::Serialize, serde::Deserialize)]
102#[serde(tag = "kind", rename_all = "snake_case")]
103pub enum ToolOutputContract {
104    #[default]
105    Static,
106    FromInputSchema {
107        input_field: String,
108        #[serde(default, skip_serializing_if = "Option::is_none")]
109        default_schema: Option<serde_json::Value>,
110    },
111}
112
113impl ToolOutputContract {
114    pub fn from_input_schema(
115        input_field: impl Into<String>,
116        default_schema: Option<serde_json::Value>,
117    ) -> Self {
118        Self::FromInputSchema {
119            input_field: input_field.into(),
120            default_schema,
121        }
122    }
123
124    pub fn is_static(&self) -> bool {
125        matches!(self, Self::Static)
126    }
127
128    fn return_type_label(&self, static_schema: &serde_json::Value) -> String {
129        match self {
130            Self::Static => compact_schema_label(static_schema),
131            Self::FromInputSchema { .. } => "T".to_string(),
132        }
133    }
134
135    fn type_parameter_suffix(&self) -> Option<String> {
136        match self {
137            Self::Static => None,
138            Self::FromInputSchema { default_schema, .. } => {
139                let default = default_schema
140                    .as_ref()
141                    .map(compact_schema_label)
142                    .unwrap_or_else(|| "any".to_string());
143                Some(format!("<T = {default}>"))
144            }
145        }
146    }
147
148    fn apply_type_witness_parameter(&self, params: &mut [ParameterDoc]) {
149        let Self::FromInputSchema { input_field, .. } = self else {
150            return;
151        };
152        if let Some(param) = params.iter_mut().find(|param| param.name == *input_field) {
153            param.type_label = "TypeSpec<T>".to_string();
154            param.nullable = false;
155            param.default_value = None;
156            param.enum_values.clear();
157            param.minimum = None;
158            param.maximum = None;
159            param.min_length = None;
160            param.max_length = None;
161            param.min_items = None;
162            param.max_items = None;
163            param.item_type = None;
164        }
165    }
166
167    fn return_fields(&self, static_schema: &serde_json::Value) -> Vec<serde_json::Value> {
168        match self {
169            Self::Static => return_field_metadata(static_schema),
170            Self::FromInputSchema { .. } => Vec::new(),
171        }
172    }
173}
174
175#[derive(Clone, Debug, Default, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
176#[serde(tag = "kind", rename_all = "snake_case")]
177pub enum ToolArgumentProjectionPolicy {
178    #[default]
179    MaterializeProjectedValues,
180    PreserveProjectedRefsInField {
181        field: String,
182    },
183}
184
185impl ToolArgumentProjectionPolicy {
186    pub fn preserve_projected_refs_in_field(field: impl Into<String>) -> Self {
187        Self::PreserveProjectedRefsInField {
188            field: field.into(),
189        }
190    }
191
192    pub fn is_materialize_projected_values(&self) -> bool {
193        matches!(self, Self::MaterializeProjectedValues)
194    }
195}
196
197fn is_default_tool_argument_projection_policy(policy: &ToolArgumentProjectionPolicy) -> bool {
198    policy.is_materialize_projected_values()
199}
200
201#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, serde::Serialize)]
202#[serde(transparent)]
203pub struct ToolId(String);
204
205impl ToolId {
206    pub fn new(id: impl Into<String>) -> Self {
207        let id = id.into();
208        assert!(!id.trim().is_empty(), "tool id must not be empty");
209        Self(id)
210    }
211
212    pub fn as_str(&self) -> &str {
213        &self.0
214    }
215}
216
217impl<'de> serde::Deserialize<'de> for ToolId {
218    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
219    where
220        D: serde::Deserializer<'de>,
221    {
222        let id = <String as serde::Deserialize>::deserialize(deserializer)?;
223        if id.trim().is_empty() {
224            return Err(serde::de::Error::custom("tool id must not be empty"));
225        }
226        Ok(Self(id))
227    }
228}
229
230impl From<String> for ToolId {
231    fn from(id: String) -> Self {
232        Self::new(id)
233    }
234}
235
236impl From<&str> for ToolId {
237    fn from(id: &str) -> Self {
238        Self::new(id)
239    }
240}
241
242impl std::fmt::Display for ToolId {
243    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
244        f.write_str(&self.0)
245    }
246}
247
248/// Tool metadata exposed to prompts, catalogs, and UI. Catalog membership —
249/// being present in a [`ToolProvider`]'s manifest list — is the execution gate;
250/// there is no per-manifest tier. The optional compact contract is the
251/// catalog-facing projection of the resolved contract; full schemas stay in
252/// [`ToolContract`].
253#[derive(Clone, Debug, PartialEq, serde::Serialize, serde::Deserialize)]
254pub struct ToolManifest {
255    pub id: ToolId,
256    pub name: String,
257    #[serde(default, skip_serializing_if = "String::is_empty")]
258    pub description: String,
259    #[serde(default, skip_serializing_if = "Option::is_none")]
260    pub compact_contract: Option<CompactToolContract>,
261    #[serde(default, skip_serializing_if = "is_default_tool_activation")]
262    pub activation: ToolActivation,
263    #[serde(default, skip_serializing_if = "std::collections::BTreeMap::is_empty")]
264    pub bindings: std::collections::BTreeMap<String, serde_json::Value>,
265    #[serde(
266        default,
267        skip_serializing_if = "is_default_tool_argument_projection_policy"
268    )]
269    pub argument_projection: ToolArgumentProjectionPolicy,
270    #[serde(
271        default = "default_tool_retry_policy",
272        skip_serializing_if = "is_default_tool_retry_policy"
273    )]
274    pub retry_policy: ToolRetryPolicy,
275}
276
277/// Heavy tool contract resolved only when a prompt or call needs schemas/docs.
278#[derive(Clone, Debug, serde::Serialize, serde::Deserialize)]
279pub struct ToolContract {
280    #[serde(default = "ToolContract::default_input_schema_contract")]
281    pub input_schema: SchemaContract,
282    #[serde(default)]
283    pub output_schema: SchemaContract,
284    #[serde(default, skip_serializing_if = "ToolOutputContract::is_static")]
285    pub output_contract: ToolOutputContract,
286    #[serde(default, skip_serializing_if = "Vec::is_empty")]
287    pub examples: Vec<String>,
288}
289
290impl Default for ToolContract {
291    fn default() -> Self {
292        Self {
293            input_schema: Self::default_input_schema_contract(),
294            output_schema: serde_json::Value::Null.into(),
295            output_contract: ToolOutputContract::Static,
296            examples: Vec::new(),
297        }
298    }
299}
300
301impl ToolContract {
302    fn default_input_schema_contract() -> SchemaContract {
303        Self::default_input_schema().into()
304    }
305
306    pub fn default_input_schema() -> serde_json::Value {
307        serde_json::json!({
308            "type": "object",
309            "properties": {},
310            "additionalProperties": true
311        })
312    }
313
314    pub fn compact_contract(&self, manifest: &ToolManifest) -> CompactToolContract {
315        self.compact_contract_with_example_limit(manifest, COMPACT_TOOL_EXAMPLE_LIMIT)
316    }
317
318    pub fn compact_contract_with_example_limit(
319        &self,
320        manifest: &ToolManifest,
321        example_limit: usize,
322    ) -> CompactToolContract {
323        self.compact_contract_with_signature_name_and_example_limit(
324            manifest,
325            &manifest.name,
326            example_limit,
327        )
328    }
329
330    pub fn compact_contract_with_signature_name(
331        &self,
332        manifest: &ToolManifest,
333        signature_name: &str,
334    ) -> CompactToolContract {
335        self.compact_contract_with_signature_name_and_example_limit(
336            manifest,
337            signature_name,
338            COMPACT_TOOL_EXAMPLE_LIMIT,
339        )
340    }
341
342    pub fn compact_contract_with_signature_name_and_example_limit(
343        &self,
344        manifest: &ToolManifest,
345        signature_name: &str,
346        example_limit: usize,
347    ) -> CompactToolContract {
348        CompactToolContract {
349            name: signature_name.to_string(),
350            signature: self.input_signature_with_name(manifest, signature_name),
351            returns: self.output_summary(),
352            parameters: self.parameter_metadata(),
353            return_fields: self
354                .output_contract
355                .return_fields(self.output_schema.canonical()),
356            description: manifest.description.trim().to_string(),
357            examples: compact_examples(&self.examples, example_limit),
358        }
359    }
360
361    pub fn input_signature(&self, manifest: &ToolManifest) -> String {
362        self.input_signature_with_name(manifest, &manifest.name)
363    }
364
365    pub fn input_signature_with_name(
366        &self,
367        _manifest: &ToolManifest,
368        signature_name: &str,
369    ) -> String {
370        let params = self
371            .parameter_docs()
372            .into_iter()
373            .map(|p| p.signature_fragment())
374            .collect::<Vec<_>>();
375        let body = if params.is_empty() {
376            "{}".to_string()
377        } else {
378            format!("{{ {} }}", params.join(", "))
379        };
380        format!(
381            "{}{}({})",
382            signature_name,
383            self.output_contract
384                .type_parameter_suffix()
385                .unwrap_or_default(),
386            body
387        )
388    }
389
390    pub fn output_summary(&self) -> String {
391        self.output_contract
392            .return_type_label(self.output_schema.canonical())
393    }
394
395    pub fn parameter_metadata(&self) -> Vec<serde_json::Value> {
396        self.parameter_docs()
397            .into_iter()
398            .map(|param| param.into_value())
399            .collect()
400    }
401
402    pub fn model_tool(&self, manifest: &ToolManifest) -> ModelTool {
403        ModelTool {
404            name: manifest.name.clone(),
405            description: manifest.description.clone(),
406            input_schema: self.input_schema.clone(),
407            output_schema: self.output_schema.clone(),
408        }
409    }
410
411    fn parameter_docs(&self) -> Vec<ParameterDoc> {
412        let mut params = schema_parameter_docs(self.input_schema.canonical());
413        self.output_contract
414            .apply_type_witness_parameter(&mut params);
415        params
416    }
417}
418
419/// Static authoring helper for tools.
420///
421/// Composes the runtime [`ToolManifest`] and [`ToolContract`] projections. Both
422/// are `#[serde(flatten)]`ed so the serialized JSON shape stays flat (and wire/
423/// persistence compatible); the two structs have disjoint field names.
424#[derive(Clone, Debug, serde::Serialize, serde::Deserialize)]
425pub struct ToolDefinition {
426    #[serde(flatten)]
427    pub manifest: ToolManifest,
428    #[serde(flatten)]
429    pub contract: ToolContract,
430}
431
432#[derive(Clone, Debug, PartialEq, Eq)]
433pub struct ModelTool {
434    pub name: String,
435    pub description: String,
436    pub input_schema: SchemaContract,
437    pub output_schema: SchemaContract,
438}
439
440const COMPACT_TOOL_EXAMPLE_LIMIT: usize = 2;
441const COMPACT_TOOL_EXAMPLE_CHAR_LIMIT: usize = 240;
442
443#[derive(Clone, Debug, PartialEq, serde::Serialize, serde::Deserialize)]
444pub struct CompactToolContract {
445    pub name: String,
446    pub signature: String,
447    pub returns: String,
448    #[serde(default, skip_serializing_if = "Vec::is_empty")]
449    pub parameters: Vec<serde_json::Value>,
450    #[serde(default, skip_serializing_if = "Vec::is_empty")]
451    pub return_fields: Vec<serde_json::Value>,
452    #[serde(default, skip_serializing_if = "String::is_empty")]
453    pub description: String,
454    #[serde(default, skip_serializing_if = "Vec::is_empty")]
455    pub examples: Vec<String>,
456}
457
458impl CompactToolContract {
459    pub fn render_signature_head(&self) -> String {
460        format!("{} -> {}", self.signature.trim(), self.returns.trim())
461    }
462
463    pub fn render_signature(&self) -> String {
464        let mut sections = vec![self.render_signature_head()];
465        let parameter_lines = self
466            .parameters
467            .iter()
468            .filter_map(compact_doc_line)
469            .collect::<Vec<_>>();
470        if !parameter_lines.is_empty() {
471            sections.push(format!("Parameters:\n{}", parameter_lines.join("\n")));
472        }
473        let return_field_lines = self
474            .return_fields
475            .iter()
476            .filter_map(compact_doc_line)
477            .collect::<Vec<_>>();
478        if !return_field_lines.is_empty() {
479            sections.push(format!("Return fields:\n{}", return_field_lines.join("\n")));
480        }
481        sections.join("\n")
482    }
483
484    pub fn render_returns(&self) -> String {
485        let mut sections = Vec::new();
486        let return_field_lines = self
487            .return_fields
488            .iter()
489            .filter_map(compact_doc_line)
490            .collect::<Vec<_>>();
491        if !return_field_lines.is_empty() {
492            sections.push(format!("Return fields:\n{}", return_field_lines.join("\n")));
493        }
494        sections.join("\n")
495    }
496
497    pub fn render_markdown(&self) -> String {
498        let mut sections = vec![format!("### {}", self.render_signature_head())];
499        if !self.description.trim().is_empty() {
500            sections.push(self.description.trim().to_string());
501        }
502        if !self.parameters.is_empty() {
503            sections.push(format!(
504                "Parameters:\n{}",
505                self.parameters
506                    .iter()
507                    .filter_map(compact_doc_line)
508                    .collect::<Vec<_>>()
509                    .join("\n")
510            ));
511        }
512        if !self.return_fields.is_empty() {
513            sections.push(format!(
514                "Return fields:\n{}",
515                self.return_fields
516                    .iter()
517                    .filter_map(compact_doc_line)
518                    .collect::<Vec<_>>()
519                    .join("\n")
520            ));
521        }
522        if !self.examples.is_empty() {
523            sections.push(format!("Examples: {}", self.examples.join("; ")));
524        }
525        sections.join("\n")
526    }
527}
528
529impl ToolDefinition {
530    pub fn raw(
531        id: impl Into<ToolId>,
532        name: impl Into<String>,
533        description: impl Into<String>,
534        input_schema: serde_json::Value,
535        output_schema: serde_json::Value,
536    ) -> Self {
537        Self {
538            manifest: ToolManifest {
539                id: id.into(),
540                name: name.into(),
541                description: description.into(),
542                compact_contract: None,
543                activation: ToolActivation::default(),
544                bindings: std::collections::BTreeMap::new(),
545                argument_projection: ToolArgumentProjectionPolicy::default(),
546                retry_policy: default_tool_retry_policy(),
547            },
548            contract: ToolContract {
549                input_schema: input_schema.into(),
550                output_schema: output_schema.into(),
551                ..ToolContract::default()
552            },
553        }
554    }
555
556    pub fn typed<Args, Output>(
557        id: impl Into<ToolId>,
558        name: impl Into<String>,
559        description: impl Into<String>,
560    ) -> Self
561    where
562        Args: schemars::JsonSchema,
563        Output: schemars::JsonSchema,
564    {
565        Self::raw(
566            id,
567            name,
568            description,
569            schema_for::<Args>(),
570            schema_for::<Output>(),
571        )
572    }
573
574    pub fn with_examples(mut self, examples: Vec<String>) -> Self {
575        self.contract.examples = examples;
576        self
577    }
578
579    pub fn with_activation(mut self, activation: ToolActivation) -> Self {
580        self.manifest.activation = activation;
581        self
582    }
583
584    pub fn with_argument_projection(
585        mut self,
586        argument_projection: ToolArgumentProjectionPolicy,
587    ) -> Self {
588        self.manifest.argument_projection = argument_projection;
589        self
590    }
591
592    pub fn with_retry_policy(mut self, retry_policy: ToolRetryPolicy) -> Self {
593        self.manifest.retry_policy = retry_policy;
594        self
595    }
596
597    pub fn with_output_contract(mut self, output_contract: ToolOutputContract) -> Self {
598        self.contract.output_contract = output_contract;
599        self
600    }
601
602    pub fn with_input_schema_projection(
603        mut self,
604        profile: impl Into<String>,
605        schema: serde_json::Value,
606    ) -> Self {
607        let profile = profile.into();
608        self.contract
609            .input_schema
610            .projection
611            .set_override(SchemaProjectionOverride::new(profile, schema));
612        self
613    }
614
615    pub fn with_output_schema_projection(
616        mut self,
617        profile: impl Into<String>,
618        schema: serde_json::Value,
619    ) -> Self {
620        let profile = profile.into();
621        self.contract
622            .output_schema
623            .projection
624            .set_override(SchemaProjectionOverride::new(profile, schema));
625        self
626    }
627
628    pub fn with_output_from_input_schema(
629        self,
630        input_field: impl Into<String>,
631        default_schema: Option<serde_json::Value>,
632    ) -> Self {
633        self.with_output_contract(ToolOutputContract::from_input_schema(
634            input_field,
635            default_schema,
636        ))
637    }
638
639    pub fn default_input_schema() -> serde_json::Value {
640        ToolContract::default_input_schema()
641    }
642
643    /// Tool identity. Read very widely, so exposed as a thin accessor over the
644    /// composed [`ToolManifest`].
645    pub fn id(&self) -> &ToolId {
646        &self.manifest.id
647    }
648
649    /// Tool name. Read very widely, so exposed as a thin accessor.
650    pub fn name(&self) -> &str {
651        &self.manifest.name
652    }
653
654    /// Tool description. Read very widely, so exposed as a thin accessor.
655    pub fn description(&self) -> &str {
656        &self.manifest.description
657    }
658
659    pub fn input_signature(&self) -> String {
660        self.contract.input_signature(&self.manifest)
661    }
662
663    pub fn output_summary(&self) -> String {
664        self.contract.output_summary()
665    }
666
667    pub fn signature(&self) -> String {
668        format!("{} -> {}", self.input_signature(), self.output_summary())
669    }
670
671    pub fn compact_contract(&self) -> CompactToolContract {
672        self.compact_contract_with_example_limit(COMPACT_TOOL_EXAMPLE_LIMIT)
673    }
674
675    pub fn compact_contract_with_example_limit(&self, example_limit: usize) -> CompactToolContract {
676        self.contract
677            .compact_contract_with_example_limit(&self.manifest, example_limit)
678    }
679
680    pub fn model_tool(&self) -> ModelTool {
681        self.contract.model_tool(&self.manifest)
682    }
683
684    /// Project the manifest, computing the catalog-facing compact contract from
685    /// the resolved [`ToolContract`].
686    pub fn manifest(&self) -> ToolManifest {
687        let mut manifest = self.manifest.clone();
688        manifest.compact_contract = Some(self.contract.compact_contract(&manifest));
689        manifest
690    }
691
692    pub fn contract(&self) -> ToolContract {
693        self.contract.clone()
694    }
695
696    /// Recompose a definition from its [`ToolManifest`] and [`ToolContract`]
697    /// projections — the inverse of [`ToolDefinition::manifest`]/[`ToolDefinition::contract`].
698    pub fn from_parts(manifest: ToolManifest, contract: ToolContract) -> Self {
699        Self { manifest, contract }
700    }
701
702    pub fn format_tool_docs(tools: &[ToolDefinition]) -> String {
703        Self::format_tool_docs_iter(tools.iter())
704    }
705
706    pub fn format_tool_docs_iter<'a>(
707        tools: impl IntoIterator<Item = &'a ToolDefinition>,
708    ) -> String {
709        tools
710            .into_iter()
711            .map(|tool| tool.compact_contract().render_markdown())
712            .collect::<Vec<_>>()
713            .join("\n\n")
714    }
715
716    pub fn parameter_metadata(&self) -> Vec<serde_json::Value> {
717        self.parameter_docs()
718            .into_iter()
719            .map(|param| param.into_value())
720            .collect()
721    }
722
723    fn parameter_docs(&self) -> Vec<ParameterDoc> {
724        let mut params = schema_parameter_docs(self.contract.input_schema.canonical());
725        self.contract
726            .output_contract
727            .apply_type_witness_parameter(&mut params);
728        params
729    }
730}
731
732mod schema_docs;
733pub use schema_docs::schema_for;
734use schema_docs::{
735    ParameterDoc, compact_doc_line, compact_examples, compact_schema_label, return_field_metadata,
736    schema_parameter_docs,
737};
738
739mod schema_validation;
740pub use schema_validation::{LashSchema, validate_tool_input};
741
742include!("tool_contract/tests.rs");
lash_sansio/tool_contract.rs

lash_sansio/
tool_contract.rs
