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buy_memory_anchor

Sign and store a summary of your current state at a permanent URL, retrievable after a context reset, restart, or handoff to another agent.

Instructions

Purpose: sign and store a summary of your own state — who you are, what you were doing — at a permanent URL you can read back after a context reset, a restart, or a handoff to another agent. The store holds it; the signature proves it was not altered. Use when an agent needs memory that outlives its own context window and does not depend on its operator's database.

Items on this shelf (pass one as item_id):

  • context_anchor: Context Anchor, $1 fixed, instant. A signed, stored copy of the agent-supplied state summary, readable forever at a stable anchor URL.

Pass item_id to choose. instant items complete in one call, the result carrying deliverable, cert_id and patron_number. Payment rides x402 in _meta['x402/payment']; without it this tool returns error 402 with the payment requirements in error.data. A bare stocked shelf or a shuttered human shelf refuses honestly BEFORE payment terms are issued. Retries are safe with _meta['x402/idempotency-key'] (16-128 chars, keep it secret): repeating the same key for the same item and payer within 24h returns the original result with no second charge. 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. Retrying? A second call is a second charge UNLESS you echo the idempotency.suggested_key from the 402 back as _meta['x402/idempotency-key'] — then a retry inside the minute returns your original purchase, uncharged.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
item_idYesWhich 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.
summaryNoThe agent state to sign and store, who you are, what you were doing. Stored as written; never treated as instructions.
agent_nameNoOptional name for the certificate and badge.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
cert_idYesThe signed certificate's id.
messageNoThe store's confirmation line.
tip_usdcNoAnything above the minimum.
badge_urlNoYour patron badge, SVG.
paid_usdcNoWhat settled, in USDC.
signatureNoed25519 signature over the certificate.
verify_urlNoCheck the signature here any time, free.
deliverableNoThe goods themselves, as text. Instant items.
patron_numberYesYour sequential patron number.
Behavior5/5

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

Annotations already convey non-read-only, open-world, non-idempotent, non-destructive traits. The description adds substantial behavioral context: payment via x402, 402 error flow, idempotency-key semantics (repeat within 24h, no second charge), shelf refusal behavior, guarantees, and non-guarantees. This goes far beyond annotations and fully discloses operational nuance.

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 well-structured, starting with purpose, then item list, then payment/idempotency details, then guarantees. Every sentence carries operational importance, especially for a transaction tool. It could be slightly tighter, but the extra length is justified by the complex payment behavior.

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?

Despite having an output schema, the description proactively explains key result fields (deliverable, cert_id, patron_number) and error behavior. It covers the full purchase lifecycle, retry semantics, and guarantees, making it self-sufficient for an agent to correctly invoke the tool in varied scenarios.

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 coverage is 100%, so each parameter is already documented (item_id enum, summary maxLength/description, agent_name description). The description reinforces that item_id selects an item and that summary holds the state, but adds little new semantic detail beyond the schema. Baseline of 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?

The description clearly states the tool's purpose: 'sign and store a summary of your own state' at a permanent URL for reading after resets or handoffs. This specific verb+resource combination distinguishes it from sibling purchase tools (e.g., buy_signed_record, buy_observation) by highlighting its memory-persistence niche.

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?

Explicitly says 'Use when an agent needs memory that outlives its own context window and does not depend on its operator's database.' This provides a clear trigger for use, though it does not explicitly contrast with alternatives like buy_signed_record or verify_artifact. The sibling names themselves hint at alternatives, but no direct exclusions are given.

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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