Generate a SHA-256 or SHA-512 digest in hexadecimal or Base64 form.
| Name | Required | Description | Default |
|---|---|---|---|
| text | Yes | Input text, up to 100 KB. | |
| encoding | No | Output encoding. Default hex. | |
| algorithm | No | Hash algorithm. Default sha256. | |
| l402_proof | No | L402 payment proof "<macaroon>:<preimage>". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set. |
Changes observed during successful MCP inspections.
Input schema / properties / l402_proof / descriptionPrevious value: -"L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 5 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."New value: +"L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 0 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set."Input schema / properties / l402_proofAdded value: +{
+ "description": "L402 payment proof \"<macaroon>:<preimage>\". Omit on the first call; an unpaid call returns a 5 sat Lightning invoice and the macaroon. Pay the invoice, then repeat the call with this argument set.",
+ "type": "string"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds only that output is a hexadecimal or Base64 digest; it says nothing about the L402 payment flow, which is the most consequential behavioral trait of this tool and appears only in the schema's l402_proof parameter.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
A single front-loaded sentence with zero filler; the resource and both option families are stated up front.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple deterministic hash tool this is nearly adequate, and there is no output schema to explain. However, the description omits the paid-call/L402 flow that will surprise an agent on first invocation, and does not state that output is a single digest string.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, including enum values for encoding and algorithm and the detailed L402 payment instructions, so the schema does the heavy lifting. The description merely restates the algorithm and encoding choices already enumerated in the schema, adding no new meaning.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description names a specific verb+resource (generate a SHA-256/SHA-512 digest) plus the output representations, which distinguishes it from siblings like base64_convert and uuid_generate without needing to name them. It doesn't explicitly contrast with siblings, so it falls short of a 5.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
There is no when-to-use guidance, no mention of alternatives such as base64_convert, and no note of prerequisites. The agent must infer usage entirely from the name and schema.
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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