Hash Encoding Direct Credits

SHA-256

hash_sha256

Destructive

Create an unkeyed SHA-256 fingerprint of UTF-8 text. Use this for checksums, deduplication, content fingerprints, or integrity comparisons when no shared secret is involved; use hmac_sha256 instead when keyed authentication is required. Returns the 32-byte digest as 64 lowercase hexadecimal characters. Costs 1 credit.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`input`	Yes	Text to hash, interpreted as UTF-8, maximum 65,536 characters.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedOct 7, 2026

addedInput schema / properties / input / description

Added value: +"Text to hash, interpreted as UTF-8, maximum 65,536 characters."

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "anyOf": [
+    {
+      "additionalProperties": false,
+      "properties": {
+        "creditsRemaining": {
+          "description": "Credits remaining after this successful 1-credit call.",
+          "maximum": 9007199254740991,
+          "minimum": 0,
+          "type": "integer"
+        },
+        "sha256": {
+          "description": "SHA-256 digest as 64 lowercase hexadecimal characters.",
+          "pattern": "^[0-9a-f]{64}$",
+          "type": "string"
+        }
+      },
+      "required": [
+        "sha256",
+        "creditsRemaining"
+      ],
+      "type": "object"
+    },
+    {
+      "additionalProperties": false,
+      "properties": {
+        "creditsRemaining": {
+          "anyOf": [
+            {
+              "maximum": 9007199254740991,
+              "minimum": 0,
+              "type": "integer"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "description": "Known remaining credits, or null when no balance can be reported."
+        },
+        "error": {
+          "description": "Human-readable reason the protected tool call failed.",
+          "type": "string"
+        },
+        "status": {
+          "description": "HTTP-style status code for the failure.",
+          "maximum": 9007199254740991,
+          "minimum": -9007199254740991,
+          "type": "integer"
+        }
+      },
+      "required": [
+        "error",
+        "status",
+        "creditsRemaining"
+      ],
+      "type": "object"
+    }
+  ],
+  "type": "object"
+}

First observedOct 7, 2026

TDQS

A3.8/5.0

Behavior1/5

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

Annotations declare destructiveHint=true, readOnlyHint=false, and idempotentHint=false, but the description describes an unkeyed fingerprint computation that returns a digest, which is inherently non-destructive, read-only, and idempotent. This is an annotation contradiction, so the rubric requires a score of 1 despite the useful output-format and cost notes.

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

Conciseness5/5

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

Four short sentences are front-loaded with purpose, then usage and the sibling alternative, then output format and cost. Every sentence earns its place and nothing is redundant.

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

Completeness4/5

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

For a simple single-parameter pure function with an output schema, the description covers purpose, usage, the hmac_sha256 alternative, return format, and credit cost. It lacks an explicit read-only/non-destructive clarification that would counter the contradictory annotations, leaving a small but important gap.

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 only parameter, input, is already fully described in the schema as UTF-8 text with a 65,536-character maximum. The description restates UTF-8 but adds no new syntax, format, or constraint details beyond the schema; with 100% schema description coverage, the baseline is 3.

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?

Names a specific verb (Create) and resource (unkeyed SHA-256 fingerprint of UTF-8 text), and distinguishes itself from hmac_sha256 by specifying that no shared secret is involved. An agent can identify the operation without opening the 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?

Gives explicit scenarios for use (checksums, deduplication, content fingerprints, integrity comparisons) and names the alternative hmac_sha256 with the condition that selects it (keyed authentication). This is exactly the when-to-use/when-not-to-use guidance needed.

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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