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caveat-lang

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caveat_test

Read-onlyIdempotent

Verify expected event outcomes and snapshot values by running scenario assertions and runtime invariant checks against inline Caveat source, with a fresh session per scenario.

Instructions

Run scenario assertions and runtime invariant checks against inline source, with a fresh session per scenario. Use to verify expected event outcomes and snapshot values; caveat_validate only checks loading, caveat_check reports diagnostics, and caveat_explain inspects history without assertions. report (caveat-scenario-report/0.1) includes files, per-scenario results/failures, check diagnostics and passed/failed totals. exitCode: 0 all passed; 1 scenario failure; 2 invalid scenario document (report has valid:false and error) or blocking authoring diagnostics. Every source reference must be inline.cav. Returns the same JSON in structuredContent and text: {schema:"caveat-authoring/0.1",operation,sourceSha256,runtime,exitCode,report}. Read exitCode even when isError is false. Bridge failures instead set isError:true with {schema:"caveat-authoring-error/0.1",error:{kind,message}}.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
sourceYesComplete inline Caveat program text, available as the virtual file inline.cav. No file path or URL lookup. At most 1 MiB of UTF-8 source; each call uses a fresh runtime.
scenariosYesScenario document object, not JSON text. Example: {"schema":"caveat-scenarios/0.1","source":"inline.cav","scenarios":[{"id":"initial","title":"Initial sequence","steps":[{"expect":{"/sequence":0}}]}]}. Each scenario needs a unique nonempty id, a title and nonempty steps. Every source reference, including optional per-scenario source, must be inline.cav. Each step has exactly one operation: send (event name; optional payload, rejected, repeat), expect (JSON Pointer-to-value map), checkpoint (state name), same_as (stored state name, with paths), resume:true, or size (save/snapshot byte bounds). Sends expect acceptance unless rejected specifies a policy message, true for any policy rejection, or an object with origin and optional code/message. Object expectations match listed members; arrays match in order; $exact, $set, $includes and $absent matchers are supported. Limits: 1 MiB serialized UTF-8 JSON, 32 scenarios, 2,000 total steps and 1,000 sends after repeat expansion.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changedv0.1.1
    • addedInput schema / properties / scenarios / description
      Added value: +"Scenario document object, not JSON text. Example: {\"schema\":\"caveat-scenarios/0.1\",\"source\":\"inline.cav\",\"scenarios\":[{\"id\":\"initial\",\"title\":\"Initial sequence\",\"steps\":[{\"expect\":{\"/sequence\":0}}]}]}. Each scenario needs a unique nonempty id, a title and nonempty steps. Every source reference, including optional per-scenario source, must be inline.cav. Each step has exactly one operation: send (event name; optional payload, rejected, repeat), expect (JSON Pointer-to-value map), checkpoint (state name), same_as (stored state name, with paths), resume:true, or size (save/snapshot byte bounds). Sends expect acceptance unless rejected specifies a policy message, true for any policy rejection, or an object with origin and optional code/message. Object expectations match listed members; arrays match in order; $exact, $set, $includes and $absent matchers are supported. Limits: 1 MiB serialized UTF-8 JSON, 32 scenarios, 2,000 total steps and 1,000 sends after repeat expansion."
    • changedInput schema / properties / source / description
      Previous value: -"Inline Caveat source; no file or URL lookup."New value: +"Complete inline Caveat program text, available as the virtual file inline.cav. No file path or URL lookup. At most 1 MiB of UTF-8 source; each call uses a fresh runtime."
  2. First observedv0.1.0

TDQS

A4.6/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare a safe read-only, idempotent, closed-world profile, and the description goes well beyond them: exitCode 0/1/2 semantics, that a valid:false report accompanies invalid documents, that exitCode must be read even when isError is false, and that bridge failures instead set isError:true with a distinct error schema. This is exactly the kind of context annotations cannot express.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the core action and sibling routing, then output contract, then error shape. Density is high and every clause carries operational information, though the repetition of limits and step details already present in the schema makes it longer than strictly necessary.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description fully carries the return contract: the report schema id and contents (files, per-scenario results/failures, diagnostics, passed/failed totals), the exitCode table, and the alternate error payload shape. An agent has everything needed to call it and interpret both success and failure responses.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% and the schema itself already documents inline.cav availability, the 1 MiB source cap, the scenario step operations, matchers and the 32-scenario/2,000-step/1,000-send limits. The description largely restates that same material rather than adding syntax or semantics the schema lacks, so the baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Run scenario assertions and runtime invariant checks against inline source') plus a key behavioral scope ('fresh session per scenario'). It explicitly separates itself from caveat_validate, caveat_check and caveat_explain, so an agent can pick it without opening any schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It says when to use it ('verify expected event outcomes and snapshot values') and then names each sibling with its contrasting purpose ('caveat_validate only checks loading, caveat_check reports diagnostics, caveat_explain inspects history without assertions'). Explicit when-to-use and when-not-to-use routing.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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