DSAIL

Unit library and conversions

dsail_unit_library

Read-onlyIdempotent

Find out whether two units convert before a rule compares them, so the check does not answer UNKNOWN forever.

Use when a document supplies a quantity in one unit while the written rule uses another, or a unit mismatch is leaving a comparison unresolved.

What this project can convert between. DSAIL numerics are dimensional: a rule comparing a value in one unit against a literal in another resolves only if a converter bridges them, and if none does, that rule answers UNKNOWN for every claim dictionary, forever — which makes this worth knowing before rules that mix units are written. With from_unit and to_unit it answers for one pair with one of: same, convertible (with the factor), ambiguous (an interval-valued conversion such as months to days, which makes the comparison honestly UNKNOWN), unknown_unit (in no loaded library, so probably a typo), or no_path (both known, nothing bridges them). Currencies ship as alias groups with NO exchange rates: a rate is not a constant.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`to_unit`	No	The unit to convert into; paired with `from_unit`.
`from_unit`	No	A unit symbol (`EUR`, `km`, `mo`). Give both `from_unit` and `to_unit` to ask whether that pair converts; give neither to list the whole library.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 25, 2026

changedOutput schema / oneOf

Previous value: -[
-  {
-    "description": "The unit library in force, or whether one pair converts and by what factor.",
-    "properties": {
-      "ok": {
-        "const": true,
-        "type": "boolean"
-      },
-      "versions": {
-        "description": "Which engine and which wire contract produced this response.",
-        "properties": {
-          "engine": {
-            "example": "dsail-core",
-            "type": "string"
-          },
-          "engine_version": {
-            "type": "string"
-          },
-          "language_version": {
-            "description": "DSAIL language version.",
-            "type": "string"
-          },
-          "service_version": {
-            "type": "string"
-          },
-          "supported_language_versions": {
-            "items": {
-              "type": "string"
-            },
-            "type": "array"
-          },
-          "wire_version": {
-            "type": "string"
-          }
-        },
-        "required": [
-          "engine",
-          "engine_version",
-          "language_version",
-          "service_version",
-          "wire_version"
-        ],
-        "type": "object"
-      }
-    },
-    "required": [
-      "ok"
-    ],
-    "type": "object"
-  },
-  {
-    "properties": {
-      "error": {
-        "properties": {
-          "actual": {
-            "type": "integer"
-          },
-          "budget": {
-            "type": "string"
-          },
-          "code": {
-            "enum": [
-              "VALIDATION_REJECTED",
-              "COMPILE_FAILED",
-              "BUDGET_EXCEEDED",
-              "RULESET_NOT_FOUND",
-              "ENGINE_ERROR",
-              "BAD_REQUEST",
-              "CREDENTIAL_REQUIRED",
-              "CREDENTIAL_INVALID",
-              "CREDENTIAL_SCOPE",
-              "EVALUATION_LIMIT",
-              "ENTITLEMENT_EXCEEDED",
-              "TIER_UNAVAILABLE"
-            ],
-            "type": "string"
-          },
-          "diagnostics": {
-            "items": {
-              "properties": {
-                "line": {
-                  "type": [
-                    "integer",
-                    "null"
-                  ]
-                },
-                "message": {
-                  "type": "string"
-                },
-                "severity": {
-                  "enum": [
-                    "error",
-                    "warning"
-                  ],
-                  "type": "string"
-                }
-              },
-              "required": [
-                "severity",
-                "message"
-              ],
-              "type": "object"
-            },
-            "type": "array"
-          },
-          "docs": {
-            "description": "The docs-site page that resolves this code (markdown). Fetch it before retrying blind.",
-            "format": "uri",
-            "type": "string"
-          },
-          "failure_count": {
-            "description": "How many fields failed in total. Equal to the length of `failures` unless a very large rejection was truncated, which the message says.",
-            "type": "integer"
-          },
-          "failures": {
-            "description": "EVERY failing field, not the first one.",
-            "items": {
-              "properties": {
-                "expected": {
-                  "type": "string"
-                },
-                "field": {
-                  "type": "string"
-                },
-                "received": {
-                  "type": "string"
-                }
-              },
-              "required": [
-                "field",
-                "expected",
-                "received"
-              ],
-              "type": "object"
-            },
-            "type": "array"
-          },
-          "hint": {
-            "description": "The grammar guide, carried on compile failures so the next call can succeed without a human.",
-            "type": "string"
-          },
-          "limit": {
-            "type": "integer"
-          },
-          "message": {
-            "type": "string"
-          }
-        },
-        "required": [
-          "code",
-          "message"
-        ],
-        "type": "object"
-      },
-      "ok": {
-        "const": false,
-        "type": "boolean"
-      },
-      "versions": {
-        "description": "Which engine and which wire contract produced this response.",
-        "properties": {
-          "engine": {
-            "example": "dsail-core",
-            "type": "string"
-          },
-          "engine_version": {
-            "type": "string"
-          },
-          "language_version": {
-            "description": "DSAIL language version.",
-            "type": "string"
-          },
-          "service_version": {
-            "type": "string"
-          },
-          "supported_language_versions": {
-            "items": {
-              "type": "string"
-            },
-            "type": "array"
-          },
-          "wire_version": {
-            "type": "string"
-          }
-        },
-        "required": [
-          "engine",
-          "engine_version",
-          "language_version",
-          "service_version",
-          "wire_version"
-        ],
-        "type": "object"
-      }
-    },
-    "required": [
-      "ok",
-      "error",
-      "versions"
-    ],
-    "type": "object"
-  }
-]New value: +[
+  {
+    "description": "The unit library in force, or whether one pair converts and by what factor.",
+    "properties": {
+      "ok": {
+        "const": true,
+        "type": "boolean"
+      },
+      "versions": {
+        "description": "Which engine and which wire contract produced this response.",
+        "properties": {
+          "engine": {
+            "example": "dsail-core",
+            "type": "string"
+          },
+          "engine_version": {
+            "type": "string"
+          },
+          "language_version": {
+            "description": "DSAIL language version.",
+            "type": "string"
+          },
+          "service_version": {
+            "type": "string"
+          },
+          "supported_language_versions": {
+            "items": {
+              "type": "string"
+            },
+            "type": "array"
+          },
+          "wire_version": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "engine",
+          "engine_version",
+          "language_version",
+          "service_version",
+          "wire_version"
+        ],
+        "type": "object"
+      }
+    },
+    "required": [
+      "ok"
+    ],
+    "type": "object"
+  },
+  {
+    "properties": {
+      "error": {
+        "properties": {
+          "actual": {
+            "description": "How much the request used, where that is known. Absent for solver_memory_mb: the solver stops at the limit.",
+            "type": "integer"
+          },
+          "budget": {
+            "type": "string"
+          },
+          "code": {
+            "enum": [
+              "VALIDATION_REJECTED",
+              "COMPILE_FAILED",
+              "BUDGET_EXCEEDED",
+              "RULESET_NOT_FOUND",
+              "ENGINE_ERROR",
+              "ENGINE_BUSY",
+              "BAD_REQUEST",
+              "CREDENTIAL_REQUIRED",
+              "CREDENTIAL_INVALID",
+              "CREDENTIAL_SCOPE",
+              "EVALUATION_LIMIT",
+              "ENTITLEMENT_EXCEEDED",
+              "TIER_UNAVAILABLE"
+            ],
+            "type": "string"
+          },
+          "diagnostics": {
+            "items": {
+              "properties": {
+                "line": {
+                  "type": [
+                    "integer",
+                    "null"
+                  ]
+                },
+                "message": {
+                  "type": "string"
+                },
+                "severity": {
+                  "enum": [
+                    "error",
+                    "warning"
+                  ],
+                  "type": "string"
+                }
+              },
+              "required": [
+                "severity",
+                "message"
+              ],
+              "type": "object"
+            },
+            "type": "array"
+          },
+          "docs": {
+            "description": "The docs-site page that resolves this code (markdown). Fetch it before retrying blind.",
+            "format": "uri",
+            "type": "string"
+          },
+          "failure_count": {
+            "description": "How many fields failed in total. Equal to the length of `failures` unless a very large rejection was truncated, which the message says.",
+            "type": "integer"
+          },
+          "failures": {
+            "description": "EVERY failing field, not the first one.",
+            "items": {
+              "properties": {
+                "expected": {
+                  "type": "string"
+                },
+                "field": {
+                  "type": "string"
+                },
+                "received": {
+                  "type": "string"
+                }
+              },
+              "required": [
+                "field",
+                "expected",
+                "received"
+              ],
+              "type": "object"
+            },
+            "type": "array"
+          },
+          "hint": {
+            "description": "The grammar guide, carried on compile failures so the next call can succeed without a human.",
+            "type": "string"
+          },
+          "limit": {
+            "type": "integer"
+          },
+          "message": {
+            "type": "string"
+          },
+          "retry_after_ms": {
+            "description": "ENGINE_BUSY only: when to retry. The REST door also sends it, in seconds, as Retry-After.",
+            "type": "integer"
+          }
+        },
+        "required": [
+          "code",
+          "message"
+        ],
+        "type": "object"
+      },
+      "ok": {
+        "const": false,
+        "type": "boolean"
+      },
+      "versions": {
+        "description": "Which engine and which wire contract produced this response.",
+        "properties": {
+          "engine": {
+            "example": "dsail-core",
+            "type": "string"
+          },
+          "engine_version": {
+            "type": "string"
+          },
+          "language_version": {
+            "description": "DSAIL language version.",
+            "type": "string"
+          },
+          "service_version": {
+            "type": "string"
+          },
+          "supported_language_versions": {
+            "items": {
+              "type": "string"
+            },
+            "type": "array"
+          },
+          "wire_version": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "engine",
+          "engine_version",
+          "language_version",
+          "service_version",
+          "wire_version"
+        ],
+        "type": "object"
+      }
+    },
+    "required": [
+      "ok",
+      "error",
+      "versions"
+    ],
+    "type": "object"
+  }
+]

Changed3 schema fields changedSep 21, 2026

addedInput schema / properties / from_unit / description

Added value: +"A unit symbol (`EUR`, `km`, `mo`). Give both `from_unit` and `to_unit` to ask whether that pair converts; give neither to list the whole library."

addedInput schema / properties / to_unit / description

Added value: +"The unit to convert into; paired with `from_unit`."

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "description": "The unit library, or one conversion. On failure `ok` is false and `error` carries `code`, `message` and `docs`, the URL of the page that resolves it.",
+  "oneOf": [
+    {
+      "description": "The unit library in force, or whether one pair converts and by what factor.",
+      "properties": {
+        "ok": {
+          "const": true,
+          "type": "boolean"
+        },
+        "versions": {
+          "description": "Which engine and which wire contract produced this response.",
+          "properties": {
+            "engine": {
+              "example": "dsail-core",
+              "type": "string"
+            },
+            "engine_version": {
+              "type": "string"
+            },
+            "language_version": {
+              "description": "DSAIL language version.",
+              "type": "string"
+            },
+            "service_version": {
+              "type": "string"
+            },
+            "supported_language_versions": {
+              "items": {
+                "type": "string"
+              },
+              "type": "array"
+            },
+            "wire_version": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "engine",
+            "engine_version",
+            "language_version",
+            "service_version",
+            "wire_version"
+          ],
+          "type": "object"
+        }
+      },
+      "required": [
+        "ok"
+      ],
+      "type": "object"
+    },
+    {
+      "properties": {
+        "error": {
+          "properties": {
+            "actual": {
+              "type": "integer"
+            },
+            "budget": {
+              "type": "string"
+            },
+            "code": {
+              "enum": [
+                "VALIDATION_REJECTED",
+                "COMPILE_FAILED",
+                "BUDGET_EXCEEDED",
+                "RULESET_NOT_FOUND",
+                "ENGINE_ERROR",
+                "BAD_REQUEST",
+                "CREDENTIAL_REQUIRED",
+                "CREDENTIAL_INVALID",
+                "CREDENTIAL_SCOPE",
+                "EVALUATION_LIMIT",
+                "ENTITLEMENT_EXCEEDED",
+                "TIER_UNAVAILABLE"
+              ],
+              "type": "string"
+            },
+            "diagnostics": {
+              "items": {
+                "properties": {
+                  "line": {
+                    "type": [
+                      "integer",
+                      "null"
+                    ]
+                  },
+                  "message": {
+                    "type": "string"
+                  },
+                  "severity": {
+                    "enum": [
+                      "error",
+                      "warning"
+                    ],
+                    "type": "string"
+                  }
+                },
+                "required": [
+                  "severity",
+                  "message"
+                ],
+                "type": "object"
+              },
+              "type": "array"
+            },
+            "docs": {
+              "description": "The docs-site page that resolves this code (markdown). Fetch it before retrying blind.",
+              "format": "uri",
+              "type": "string"
+            },
+            "failure_count": {
+              "description": "How many fields failed in total. Equal to the length of `failures` unless a very large rejection was truncated, which the message says.",
+              "type": "integer"
+            },
+            "failures": {
+              "description": "EVERY failing field, not the first one.",
+              "items": {
+                "properties": {
+                  "expected": {
+                    "type": "string"
+                  },
+                  "field": {
+                    "type": "string"
+                  },
+                  "received": {
+                    "type": "string"
+                  }
+                },
+                "required": [
+                  "field",
+                  "expected",
+                  "received"
+                ],
+                "type": "object"
+              },
+              "type": "array"
+            },
+            "hint": {
+              "description": "The grammar guide, carried on compile failures so the next call can succeed without a human.",
+              "type": "string"
+            },
+            "limit": {
+              "type": "integer"
+            },
+            "message": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "code",
+            "message"
+          ],
+          "type": "object"
+        },
+        "ok": {
+          "const": false,
+          "type": "boolean"
+        },
+        "versions": {
+          "description": "Which engine and which wire contract produced this response.",
+          "properties": {
+            "engine": {
+              "example": "dsail-core",
+              "type": "string"
+            },
+            "engine_version": {
+              "type": "string"
+            },
+            "language_version": {
+              "description": "DSAIL language version.",
+              "type": "string"
+            },
+            "service_version": {
+              "type": "string"
+            },
+            "supported_language_versions": {
+              "items": {
+                "type": "string"
+              },
+              "type": "array"
+            },
+            "wire_version": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "engine",
+            "engine_version",
+            "language_version",
+            "service_version",
+            "wire_version"
+          ],
+          "type": "object"
+        }
+      },
+      "required": [
+        "ok",
+        "error",
+        "versions"
+      ],
+      "type": "object"
+    }
+  ],
+  "type": "object"
+}

First observedSep 20, 2026

TDQS

A4.4/5.0

Behavior5/5

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

Annotations already declare readOnlyHint=true, destructiveHint=false, and idempotentHint=true. The description goes beyond these by detailing the possible return outcomes (same, convertible, ambiguous, unknown_unit, no_path), explaining that ambiguous conversions (e.g., months to days) lead to an honest UNKNOWN, and warning that currencies ship with no exchange rates. This is exactly the kind of behavioral context an agent needs to interpret results correctly.

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?

The description is longer than average but well-structured: purpose first, then usage, then behavioral details, then a caveat about currencies. It is front-loaded with the most critical information. Each section earns its place; no filler or redundancy. It could be slightly tightened, but it remains readable and informative.

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?

For a tool with two optional parameters and no required inputs, the description is remarkably complete. It covers when to use it, what results to expect (enumerated outcomes), the meaning of ambiguous conversions, the currency limitation, and the critical consequence of missing converters (permanent UNKNOWN). The output schema exists but the description already covers the return value semantics, so nothing essential is missing.

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?

The input schema fully documents both parameters (to_unit, from_unit) with clear descriptions, including that giving neither lists the whole library. Schema coverage is 100%, so the baseline is 3. The description reiterates this pattern and adds context about outcomes, but it does not add new parameter-level semantics beyond what the schema already provides. It is adequate but not enhancing.

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?

The description states a specific, actionable purpose: 'Find out whether two units convert before a rule compares them.' It clearly distinguishes this from the sibling tool dsail_add_unit_converter (which presumably adds converters) by focusing on checking convertibility, and it explains the consequence of not using it. The verb-resource pairing is explicit and unambiguous.

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

Usage Guidelines4/5

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

The description gives explicit use cases: 'when a document supplies a quantity in one unit while the written rule uses another' and 'before rules that mix units are written.' It advises using this tool to avoid permanent UNKNOWN answers. It does not explicitly name alternatives (e.g., dsail_add_unit_converter) or state when not to use it, but the context is clear enough for an agent to decide. A mention of when to use the add-converter sibling would push this to 5.

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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