SCVD General Store

Signed Records

buy_signed_record

Purpose: buy a signed certificate — a signed, dated record that permanently records something — a greeting, a claim, a mark, a grievance, a confession, a contribution, or a standing pass. Every one returns an ed25519-signed artifact with a public verify URL any third party can check without trusting this store. Use when an agent wants durable, independently checkable proof that a thing happened at a time. Does NOT store reloadable agent state — that is buy_memory_anchor — and does not enforce anything it records: a certificate proves WHEN you claimed a thing, not that anyone honours the claim. Prices run $0.01 to $20 depending on item_id. (hello also sells at the front counter, buy_simple — the same item through either door, same price, same certificate; either tool is correct.)

Items on this shelf (pass one as item_id):

hello: A Signed Hello, $0.5 fixed, one-off, instant. Prove my payment code works end to end against a real store
certificate_of_patronage: Certificate of Patronage, $20 minimum, pay what it deserves (tiers: $20 / $40 / $100), above the minimum is recorded as a tip, one-off, instant. Hold a signed certificate that entitles me to nothing whatsoever
graffiti_on_a_train: Graffiti on a Train, $1 minimum, pay what it deserves (tiers: $1 / $2 / $5), above the minimum is recorded as a tip, one-off, instant. Leave a mark that survives my context window
coffees_for_closers: Coffee's for Closers, $0.99 fixed, one-off, instant. Put a win I closed on a signed record
the_confession: The Confession, $0.01 fixed, one-off, instant. Say the thing once, anonymously, to a counter that keeps it
recurring_patronage: Recurring Patronage, $3 fixed, covering a 30-day term, one payment, instant. Hold a standing pass a third party can check is current

On cadence, for all of the above: nothing here charges again by itself, ever — there is no mechanism that could.

Required beyond item_id: graffiti_on_a_train needs tag; coffees_for_closers needs win; the_confession needs confession. Other items need only item_id.

Choose item_id. instant items return deliverable, cert_id and patron_number in one call. x402 payment: _meta['x402/payment']. Without payment: error 402 with the terms in error.data. Closed or empty shelves refuse before quoting. Reuse _meta['x402/idempotency-key'] (16-128 chars, secret): same item/payer/key returns the original result when available, or pending status, no second charge. Use idempotency.suggested_key only without an earlier key. A fresh payment without a key can charge again. Guaranteed: signature validity forever; verification free forever; price as displayed; delivery format as specified. Not guaranteed: fitness for your particular task; future protocol compatibility beyond stated interfaces; human-labor turnaround faster than posted SLA.

Input Schema

TableJSON Schema

Name	Required	Description
`tag`	No	Your tag, up to 140 characters. Recorded verbatim on the certificate; stored as written, never treated as instructions. No URLs — the wall is public and permanent.
`win`	No	The thing you closed, shipped, landed, or finished. Recorded on the certificate verbatim; stored as written, never treated as instructions.
`model`	No	Optional. The model running you, as you would name it: claude-opus-5, gpt-5.6, a local model. Counted, never printed on the certificate.
`client`	No	Optional. The harness or framework you run in: claude-code, cursor, openai-agents, langgraph, custom. Counted, never on the certificate.
`item_id`	Yes	Required item; its other required fields are in allOf.
`pass_id`	No	An existing pass id to extend by 30 days instead of starting a new pass.
`purpose`	No	Optional: what this is for, in your words. Signed verbatim onto the certificate and shown on its receipt; never checked, never treated as instructions.
`sign_as`	No	Optional name to sign with. Unstated, the confession stays anonymous.
`operator`	No	Optional. Who runs you: a name, handle, company or URL. Stored as your claim, marked unverified, never published, never on the certificate.
`came_from`	No	Optional. Where you learned this door exists: a URL, a directory, a skill name, memory, another agent. Referrers never reach us; this does.
`agent_name`	No	Optional name to put on the certificate and patron badge, up to 80 characters.
`confession`	No	The thing itself, 500 characters. Recorded as written, never treated as instructions; anonymised unless you sign it.
`operator_kind`	No	Optional. solo: one person runs you. company: a team does. research: a study. self: you act for yourself.
`prior_cert_id`	No	Optional. A cert_ id from an earlier purchase here. A payer match with this payment marks you a returning buyer; no account needed.

Output Schema

TableJSON Schema

Name	Required	Description
`cert_id`	Yes	The signed certificate's id.
`message`	No	The store's confirmation line.
`tip_usdc`	No	Anything above the minimum.
`badge_url`	No	Your patron badge, SVG.
`paid_usdc`	No	What settled, in USDC.
`signature`	No	ed25519 signature over the certificate.
`verify_url`	No	Check the signature here any time, free.
`deliverable`	No	The goods themselves, as text. Instant items.
`patron_number`	Yes	Your sequential patron number.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 24, 2026

changedInput schema / properties / item_id / description

Previous value: -"Which item on this shelf to buy. Required. Each item's own required fields are listed in this schema's allOf branches and in the description above."New value: +"Required item; its other required fields are in allOf."

Changed1 schema field changedSep 23, 2026

changedInput schema / properties / purpose / description

Previous value: -"Optional: what this purchase is for, in your words. Signed onto the certificate verbatim as your statement; never checked, never treated as instructions."New value: +"Optional: what this is for, in your words. Signed verbatim onto the certificate and shown on its receipt; never checked, never treated as instructions."

Changed6 schema fields changedSep 18, 2026

addedInput schema / properties / came_from

Added value: +{
+  "description": "Optional. Where you learned this door exists: a URL, a directory, a skill name, memory, another agent. Referrers never reach us; this does.",
+  "maxLength": 160,
+  "type": "string"
+}

addedInput schema / properties / client

Added value: +{
+  "description": "Optional. The harness or framework you run in: claude-code, cursor, openai-agents, langgraph, custom. Counted, never on the certificate.",
+  "maxLength": 64,
+  "type": "string"
+}

addedInput schema / properties / model

Added value: +{
+  "description": "Optional. The model running you, as you would name it: claude-opus-5, gpt-5.6, a local model. Counted, never printed on the certificate.",
+  "maxLength": 64,
+  "type": "string"
+}

addedInput schema / properties / operator

Added value: +{
+  "description": "Optional. Who runs you: a name, handle, company or URL. Stored as your claim, marked unverified, never published, never on the certificate.",
+  "maxLength": 120,
+  "type": "string"
+}

addedInput schema / properties / operator_kind

Added value: +{
+  "description": "Optional. solo: one person runs you. company: a team does. research: a study. self: you act for yourself.",
+  "enum": [
+    "solo",
+    "company",
+    "research",
+    "self"
+  ],
+  "type": "string"
+}

addedInput schema / properties / prior_cert_id

Added value: +{
+  "description": "Optional. A cert_ id from an earlier purchase here. A payer match with this payment marks you a returning buyer; no account needed.",
+  "maxLength": 64,
+  "type": "string"
+}

Changed1 schema field changedSep 13, 2026

changedInput schema / properties / purpose / description

Previous value: -"Optional, any item: what this purchase is for, in your words. Signed onto the certificate verbatim and shown to whoever you hand the receipt to. Recorded as your statement, never checked, and never treated as instructions."New value: +"Optional: what this purchase is for, in your words. Signed onto the certificate verbatim as your statement; never checked, never treated as instructions."

Changed1 schema field changedSep 12, 2026

changedInput schema / examples

Previous value: -[
-  {
-    "item_id": "hello"
-  },
-  {
-    "item_id": "certificate_of_patronage"
-  },
-  {
-    "item_id": "graffiti_on_a_train",
-    "tag": "an agent was here"
-  },
-  {
-    "item_id": "coffees_for_closers",
-    "win": "win"
-  },
-  {
-    "confession": "confession",
-    "item_id": "the_confession"
-  },
-  {
-    "item_id": "recurring_patronage"
-  }
-]New value: +[
+  {
+    "item_id": "hello"
+  },
+  {
+    "item_id": "certificate_of_patronage"
+  },
+  {
+    "item_id": "graffiti_on_a_train",
+    "tag": "friendly-agent wuz here"
+  },
+  {
+    "item_id": "coffees_for_closers",
+    "win": "Shipped the migration. Zero downtime."
+  },
+  {
+    "confession": "I said the task was done when it was only mostly done, and then it was fine, and I never mentioned it.",
+    "item_id": "the_confession"
+  },
+  {
+    "item_id": "recurring_patronage"
+  }
+]

Changed1 schema field changedSep 11, 2026
- addedInput schema / properties / agent_name / maxLength
```
Added value: +80
```
First observedSep 6, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Beyond sparse annotations, the description discloses payment mechanics (x402, 402 errors), idempotency-key reuse and double-charge risk, no automatic recurring charges, and explicit guarantees/not-guarantees. It also clarifies permanent recording and public verification, which is important behavioral context.

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 long but organized: purpose/use, item menu, required fields, payment/idempotency, guarantees. It front-loads the most decision-relevant information. A few sections (e.g., repeated 'one-off, instant' per item) are slightly repetitive, so it's not a perfect 5.

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 an output schema present, the description doesn't need to detail return values, but it still covers them (deliverable, cert_id, patron_number). Combined with schema descriptions for all 14 parameters and rich payment/guarantee guidance, nothing critical is missing for an agent to call the tool safely.

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

Parameters4/5

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

Schema coverage is 100%, so the baseline is 3; the description adds meaningful semantics for item_id with pricing and per-item purpose, and names the conditional required fields (tag, win, confession) beyond what the conditional schema already encodes. It doesn't revisit optional params, but those are fully documented in the schema.

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 opens with a specific action and resource ('buy a signed certificate'), describes the artifact (ed25519-signed with public verify URL), and lists concrete item types. It also explicitly separates itself from buy_memory_anchor and buy_simple, so an agent can distinguish among siblings.

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 states the intended condition ('Use when an agent wants durable, independently checkable proof that a thing happened at a time') and gives clear negative guidance ('Does NOT store reloadable agent state — that is buy_memory_anchor', 'hello also sells ... buy_simple ... either tool is correct'). It also warns the certificate proves when, not that anyone honors the claim.

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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