Stannp

Stannp is a direct mail platform that enables businesses to send physical postcards and letters programmatically via a REST API. The platform lets developers create campaigns, upload recipient lists, trigger individual mail pieces in real time, and track print and delivery status through webhooks and event endpoints. Authentication uses API key-based HTTP Basic Auth over HTTPS, and the API follows a simple JSON response envelope with success/data or success/error fields. Stannp serves businesses across the UK, US, and Canada with per-item pricing for letters and postcards at scale, and supports no-code integrations through Zapier and Make as well as official SDKs for PHP, Go, and C#.

Stannp publishes 7 API contracts indexed on the APIs.io network, including Account API, Campaigns API, Events API, and 4 more. Tagged areas include Direct Mail, Postcards, Letters, Print, and Physical Mail.

The Stannp catalog on APIs.io includes 1 event-driven AsyncAPI specification, 1 JSON-LD context, and 1 Spectral governance ruleset.

Stannp’s developer surface includes authentication, sandbox, documentation, API reference, getting-started guide, support, engineering blog, and 35 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

74.7/100 exemplar ▬ flat Agent 40/100 agent native saas Full breakdown ↓
scored 2026-10-23 · rubric v0.25.0 · Show this score on your site →

AccessFreemiumSelf serve⚡ Free to try

1 published contract

Direct Mail Postcards Letters Print Physical Mail Marketing Automation Campaigns Address Verification SMS Webhook Mailing Lists Fulfillment

What this lets a business do 1

Business capabilities this provider's published APIs can perform, derived from its own contracts. Browse all capabilities →

Marketing Management

BC-400

Campaigns

POST /campaigns/create POST /campaigns/approve POST /campaigns/book

What people ask Stannp 7

The questions people put to an LLM, and the jobs they hand an agent, that Stannp's APIs answer — each one linked to the operation that does it. Generated by API Evangelist

Stannp Campaigns API List direct mail campaigns “What mail campaigns have I created so far?” Look up a campaign “What are the settings and status of one particular campaign?” Create a direct mail campaign for a group “How do I set up a bulk mailing to everyone in one of my recipient groups?” Generate a sample PDF of a campaign “Can I see a proof of what a campaign's mailpiece will look like before approving it?”

Stannp Groups API List recipient groups “What mailing groups have I set up?” Create a recipient group “How do I set up a new mailing list group to hold recipients?” Add existing recipients to a group “Can I put recipients I've already created into another mailing group?” Remove specific recipients from a group “How can I take a few people out of a mailing group without deleting them?”

Stannp Recipients API List recipients “Who is on my mailing list?” Look up a single recipient “What address do I have on file for a specific recipient?” Add a recipient address “How do I add one new person's postal address to my mailing list?” Delete a recipient “How do I permanently remove someone's address record?”

Stannp Letters API Send a letter from a template or HTML “How do I mail a single letter built from one of my saved templates?” Mail a pre-merged PDF letter “Can I upload a finished PDF with the address already on it and have it posted?” Look up a letter mailpiece “What's the current status of a letter I sent?” Cancel a letter before dispatch “Can I stop a letter from going out if it hasn't been dispatched yet?”

Stannp Postcards API Send a postcard “How do I mail a single postcard with my own front and back artwork?” Look up a postcard mailpiece “What's the status of a postcard I already sent?” Cancel a postcard before dispatch “Can I cancel a postcard that hasn't been dispatched yet?”

Stannp Account API Check the account balance “How much credit is left on my Stannp account?” Add funds to the account balance “Can I prepay credit onto my account so mailings draw from a balance?” Look up the signed-in user “Which user is my API key authenticated as?”

Stannp Events API Record an engagement event for a recipient “How do I log that a mail recipient made a purchase after receiving a mailpiece?”

Kin Score

Kin Score How this is scored →
scored 2026-10-23 · rubric v0.25.0

Composite quality — 74.7/100 · exemplar

Contract Quality 13.0 / 19

Developer Ergonomics 11.2 / 15

Access Clarity 12.8 / 15

Operational Transparency 6.7 / 10

Contract Governance 3.8 / 9

Discoverability 5.5 / 8

Regulatory Posture 5.1 / 15

Create-or-Update Ergonomics 2.8 / 10

Agent readiness — 40/100 · agent native

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 6 / 6

MCP Server 0 / 12

Machine-Readable Auth 10 / 10

Idempotency 9 / 9

Stable Error Semantics 8 / 8

Request/Response Examples 7 / 7

Rate-Limit Signaling 7 / 7

Typed Event Surface 6 / 6

Agent Skills 5 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

Regulatory Posture applies to this provider. Its tags matched the Telecommunications regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics applies to this provider. This API accepts writes, so it carries 10 points of the composite. It is scored from the published contracts themselves: whether a caller can create-or-update in one call, whether the write accepts a key the caller already holds, and whether the response says which branch ran. Without that, every write needs a search-and-branch in front of it, and the first time that check is skipped a duplicate record is created. Scored against the observed mean rather than raw — a provider at the catalog average is unchanged by this facet, not penalised by it.

The six quality facets above are damped to 75 points between them, because the conditional facet above carries the other 25. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 75% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from github.com/api-evangelist/stannp: open an issue to ask a question, or submit a pull request to add artifacts. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Markets this provider is in provisional

The Kin Score Market layer reads a provider inside its market: its position, and how deep its integrations go. Depth is only comparable within a position. Provisional and unweighted: not part of the Kin Score or agent readiness.

Market	Position	Depth	Registered MCP server	Declares compatibility
HubSpot App Marketplace (CRM add-ons, outbound, performance marketing, chat)	undeclared	-	-	-

Registered MCP server and declares compatibility are report only — not weighted. Undeclared means we found nothing we can read, so there is no number: we never infer integrations.

APIs 7

Individual APIs this provider publishes, each with its own machine-readable definition.

Stannp Account API

Account balance and user information

Stannp Campaigns API

Manage batch direct mail campaigns

Stannp Events API

Record recipient engagement and conversion events

Stannp Groups API

Manage recipient groups

Stannp Letters API

Create, post, retrieve, and cancel letter mailpieces

Stannp Postcards API

Create, retrieve, and cancel postcard mailpieces

Stannp Recipients API

Manage individual recipients and bulk imports

OPEN COLLECTION

Scroll for all 7

Pricing Plans 1

Published pricing tiers and plan structures.

Stannp Plans Pricing

5 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Stannp Rate Limits

4 limits

RATE LIMITS

FinOps 1

Cost, billing, and metering signals for API financial operations.

Stannp Finops

FINOPS

Event Specifications 1

AsyncAPI definitions for this provider's event-driven and streaming APIs.

Stannp Webhooks

ASYNCAPI

Semantic Vocabularies 1

JSON-LD contexts and semantic vocabularies used across these APIs.

Stannp Context

45 classes · 9 properties

JSON-LD

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

Stannp — jsonschema rules

5 rules · 4 warnings 1 info

SPECTRAL

22 properties

JSON SCHEMA

Examples 3

Example request and response payloads for these APIs.

Create Postcard Request

8 fields

EXAMPLE

Create Postcard Response

2 fields

EXAMPLE

Webhook Payload

5 fields

EXAMPLE

Security Posture 4

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Stannp Authentication

http/apiKey · 3 schemes

SECURITY

Stannp Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Stannp Vulnerability Disclosure

Hackerone · contact published

SECURITY

Stannp Trust Center

HIPAA, ISO 27001, ISO 9001, GDPR, ICO registration ZA134992 (UK Data Processor), USPS CASS certification, Royal Mail PAF accreditation, Royal Mail Mail Made Easy partner, Securi...

SECURITY

Agentic Access 1

Recommended x-agentic-access execution contracts for AI agents.

Stannp Agentic Access

32 operations · 20 acting

AGENTIC

Resources

Get Started 5

Portal, sign-up, and the first successful call

Sandbox

DeveloperPortal

GettingStarted

SignUp

Login

Documentation 2

Reference material describing how the API behaves

Documentation

Documentation

APIReference

APIReference

Agent Surfaces 4

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgenticAccess

X-MCPServerCandidate

X-MCPServerCandidate

AgentSkill

AgentSkill

LLMsTxt

LLMsTxt

Design & Contract 7

Pagination, idempotency, versioning, errors, and events

Conventions

Idempotency

ErrorCatalog

DataModel

Conformance

Lifecycle

Webhooks

Scroll for all 7

Build 4

SDKs, sample code, and the tooling you integrate with

PostmanWorkspace

PostmanWorkspace

Packages

Packages

SDKs

SDKs

GitHubOrganization

GitHubOrganization

Access & Security 6

Authentication, authorization, and security posture

TrustCenter

TrustCenter

Compliance

Compliance

DomainSecurity

DomainSecurity

VulnerabilityDisclosure

VulnerabilityDisclosure

Security

Security

Authentication

Authentication

Operate 4

Status, limits, changes, and where to get help

StatusPage

Support

HelpCenter

RateLimits

Commercial 5

Pricing, plans, and the legal terms of use

Pricing

Plans

TermsOfService

PrivacyPolicy

FinOps

Company 3

The organization behind the API

Website

Website

LinkedIn

Blog

Blog

Other 2

Properties that don't map to a standard resource type

CapabilityMap

CapabilityMap

Source (apis.yml)

aid: stannp
name: Stannp
description: 'Stannp is a direct mail platform that enables businesses to send physical postcards and letters programmatically
  via a REST API. The platform lets developers create campaigns, upload recipient lists, trigger individual mail pieces in
  real time, and track print and delivery status through webhooks and event endpoints. Authentication uses API key-based HTTP
  Basic Auth over HTTPS, and the API follows a simple JSON response envelope with success/data or success/error fields. Stannp
  serves businesses across the UK, US, and Canada with per-item pricing for letters and postcards at scale, and supports no-code
  integrations through Zapier and Make as well as official SDKs for PHP, Go, and C#.

  '
type: Index
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: true
  label: Hosted service · you call their endpoint
  confidence: high
  source:
  - openapi
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: freemium
  onboarding: self-serve
  trial: false
  try_now: true
  public: false
  label: Freemium · Self-serve signup
  confidence: high
  source:
  - plans
  - authentication
  - rate-limits
  - security
  - sandbox
  generated: '2026-09-03'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/stannp.png
tags:
- Direct Mail
- Postcards
- Letters
- Print
- Physical Mail
- Marketing Automation
- Campaigns
- Address Verification
- SMS
- Webhook
- Mailing Lists
- Fulfillment
tags_raw:
- Direct Mail
- Postcards
- Letters
- Print
- Physical Mail
- Marketing Automation
- Campaigns
- Address Verification
- SMS
- Webhooks
- Mailing Lists
- Fulfillment
url: https://raw.githubusercontent.com/api-evangelist/stannp/refs/heads/main/apis.yml
created: '2026-06-12'
modified: '2026-08-13'
specificationVersion: '0.23'
apis:
- aid: stannp:stannp-account-api
  name: Stannp Account API
  description: Account balance and user information
  humanURL: https://www.stannp.com/us/direct-mail-api
  baseURL: https://api-us1.stannp.com/v1
  tags:
  - Account
  properties:
  - type: OpenAPI
    url: openapi/stannp-account-api-openapi.yml
  - type: Overlay
    url: overlays/stannp-account-api-overlay.yaml
  - type: Documentation
    url: https://www.stannp.com/us/direct-mail-api/guide
  - type: JSONSchema
    url: json-schema/recipient.json
  - type: JSONSchema
    url: json-schema/mailpiece.json
  - type: JSONSchema
    url: json-schema/campaign.json
  - type: Vocabulary
    url: vocabulary/stannp-vocabulary.yml
  - type: JSONLDContext
    url: json-ld/stannp-context.jsonld
- aid: stannp:stannp-campaigns-api
  name: Stannp Campaigns API
  description: Manage batch direct mail campaigns
  humanURL: https://www.stannp.com/us/direct-mail-api
  baseURL: https://api-us1.stannp.com/v1
  tags:
  - Campaigns
  properties:
  - type: OpenAPI
    url: openapi/stannp-campaigns-api-openapi.yml
  - type: Overlay
    url: overlays/stannp-campaigns-api-overlay.yaml
  - type: AgentSkill
    url: skills/stannp-build-and-book-a-campaign.md
  - type: Documentation
    url: https://www.stannp.com/us/direct-mail-api/guide
  - type: JSONSchema
    url: json-schema/recipient.json
  - type: JSONSchema
    url: json-schema/mailpiece.json
  - type: JSONSchema
    url: json-schema/campaign.json
  - type: Vocabulary
    url: vocabulary/stannp-vocabulary.yml
  - type: JSONLDContext
    url: json-ld/stannp-context.jsonld
- aid: stannp:stannp-events-api
  name: Stannp Events API
  description: Record recipient engagement and conversion events
  humanURL: https://www.stannp.com/us/direct-mail-api
  baseURL: https://api-us1.stannp.com/v1
  tags:
  - Event
  tags_raw:
  - Events
  properties:
  - type: OpenAPI
    url: openapi/stannp-events-api-openapi.yml
  - type: Overlay
    url: overlays/stannp-events-api-overlay.yaml
  - type: Webhooks
    url: asyncapi/stannp-webhooks.yml
  - type: Documentation
    url: https://www.stannp.com/us/direct-mail-api/guide
  - type: JSONSchema
    url: json-schema/recipient.json
  - type: JSONSchema
    url: json-schema/mailpiece.json
  - type: JSONSchema
    url: json-schema/campaign.json
  - type: Vocabulary
    url: vocabulary/stannp-vocabulary.yml
  - type: JSONLDContext
    url: json-ld/stannp-context.jsonld
- aid: stannp:stannp-groups-api
  name: Stannp Groups API
  description: Manage recipient groups
  humanURL: https://www.stannp.com/us/direct-mail-api
  baseURL: https://api-us1.stannp.com/v1
  tags:
  - Group
  tags_raw:
  - Groups
  properties:
  - type: OpenAPI
    url: openapi/stannp-groups-api-openapi.yml
  - type: Overlay
    url: overlays/stannp-groups-api-overlay.yaml
  - type: Documentation
    url: https://www.stannp.com/us/direct-mail-api/guide
  - type: JSONSchema
    url: json-schema/recipient.json
  - type: JSONSchema
    url: json-schema/mailpiece.json
  - type: JSONSchema
    url: json-schema/campaign.json
  - type: Vocabulary
    url: vocabulary/stannp-vocabulary.yml
  - type: JSONLDContext
    url: json-ld/stannp-context.jsonld
- aid: stannp:stannp-letters-api
  name: Stannp Letters API
  description: Create, post, retrieve, and cancel letter mailpieces
  humanURL: https://www.stannp.com/us/direct-mail-api
  baseURL: https://api-us1.stannp.com/v1
  tags:
  - Letters
  properties:
  - type: OpenAPI
    url: openapi/stannp-letters-api-openapi.yml
  - type: Overlay
    url: overlays/stannp-letters-api-overlay.yaml
  - type: AgentSkill
    url: skills/stannp-send-a-transactional-letter.md
  - type: Documentation
    url: https://www.stannp.com/us/direct-mail-api/guide
  - type: JSONSchema
    url: json-schema/recipient.json
  - type: JSONSchema
    url: json-schema/mailpiece.json
  - type: JSONSchema
    url: json-schema/campaign.json
  - type: Vocabulary
    url: vocabulary/stannp-vocabulary.yml
  - type: JSONLDContext
    url: json-ld/stannp-context.jsonld
- aid: stannp:stannp-postcards-api
  name: Stannp Postcards API
  description: Create, retrieve, and cancel postcard mailpieces
  humanURL: https://www.stannp.com/us/direct-mail-api
  baseURL: https://api-us1.stannp.com/v1
  tags:
  - Postcards
  properties:
  - type: OpenAPI
    url: openapi/stannp-postcards-api-openapi.yml
  - type: Overlay
    url: overlays/stannp-postcards-api-overlay.yaml
  - type: AgentSkill
    url: skills/stannp-send-a-single-postcard.md
  - type: Documentation
    url: https://www.stannp.com/us/direct-mail-api/guide
  - type: JSONSchema
    url: json-schema/recipient.json
  - type: JSONSchema
    url: json-schema/mailpiece.json
  - type: JSONSchema
    url: json-schema/campaign.json
  - type: Vocabulary
    url: vocabulary/stannp-vocabulary.yml
  - type: JSONLDContext
    url: json-ld/stannp-context.jsonld
- aid: stannp:stannp-recipients-api
  name: Stannp Recipients API
  description: Manage individual recipients and bulk imports
  humanURL: https://www.stannp.com/us/direct-mail-api
  baseURL: https://api-us1.stannp.com/v1
  tags:
  - Recipients
  properties:
  - type: OpenAPI
    url: openapi/stannp-recipients-api-openapi.yml
  - type: Overlay
    url: overlays/stannp-recipients-api-overlay.yaml
  - type: AgentSkill
    url: skills/stannp-sync-recipients-and-track-engagement.md
  - type: Documentation
    url: https://www.stannp.com/us/direct-mail-api/guide
  - type: JSONSchema
    url: json-schema/recipient.json
  - type: JSONSchema
    url: json-schema/mailpiece.json
  - type: JSONSchema
    url: json-schema/campaign.json
  - type: Vocabulary
    url: vocabulary/stannp-vocabulary.yml
  - type: JSONLDContext
    url: json-ld/stannp-context.jsonld
common:
- type: PostmanWorkspace
  url: https://www.postman.com/kinlaneapi/stannp/overview
- type: CapabilityMap
  url: capabilities/stannp-capability-edges.yml
  name: Stannp Business Capability Map
- type: AgenticAccess
  url: agentic-access/stannp-agentic-access.yml
- type: TrustCenter
  url: security/stannp-trust-center.yml
- type: Compliance
  url: https://www.stannp.com/us/accreditations
- type: DomainSecurity
  url: security/stannp-domain-security.yml
- type: VulnerabilityDisclosure
  url: security/stannp-vulnerability-disclosure.yml
- type: Security
  url: https://www.stannp.com/us/trust
- type: Authentication
  url: authentication/stannp-authentication.yml
- type: Conventions
  url: conventions/stannp-conventions.yml
- type: Idempotency
  url: conventions/stannp-conventions.yml
- type: ErrorCatalog
  url: errors/stannp-problem-types.yml
- type: DataModel
  url: data-model/stannp-data-model.yml
- type: Conformance
  url: conformance/stannp-conformance.yml
- type: Lifecycle
  url: lifecycle/stannp-lifecycle.yml
- type: StatusPage
  url: https://status.stannp.com/
- type: Sandbox
  url: sandbox/stannp-sandbox.yml
- type: Webhooks
  url: asyncapi/stannp-webhooks.yml
- type: Packages
  url: packages/stannp-packages.yml
- type: SDKs
  url: packages/stannp-packages.yml
- type: X-MCPServerCandidate
  url: mcp/stannp-mcp.yml
  note: 'Renamed from MCPServer 2026-09-03 (roadmap#247): the manifest self-describes as status: candidate — a tool list derived
    from the published API contracts, not an existing server. The scorer already read the manifest and reported mcp_server
    correctly; the MCPServer type was crediting the artifact-type surfaces with a server that does not exist.'
- type: AgentSkill
  url: skills/_index.yml
- type: LLMsTxt
  url: llms/stannp-llms.txt
- type: Website
  url: https://www.stannp.com
- type: DeveloperPortal
  url: https://www.stannp.com/us/developer-tools
- type: Documentation
  url: https://www.stannp.com/us/direct-mail-api/guide
- type: APIReference
  url: https://www.stannp.com/us/direct-mail-api/postcards
- type: GettingStarted
  url: https://www.stannp.com/us/direct-mail-api/guide#introduction
- type: Support
  url: https://www.stannp.com/us/support
- type: HelpCenter
  url: https://knowledge.stannp.com/us
- type: Integrations
  url: https://www.stannp.com/us/integrations
- type: GitHubOrganization
  url: https://github.com/Stannp
- type: LinkedIn
  url: https://www.linkedin.com/company/stannp-com-postcard-bulk-mailer
- type: X
  url: https://twitter.com/stannpdm
- type: Blog
  url: https://go.stannp.com/en-us/blogs
- type: Pricing
  url: https://www.stannp.com/us/pricing
- type: Plans
  url: plans/stannp-plans-pricing.yml
- type: SignUp
  url: https://app-us1.stannp.com/register
- type: Login
  url: https://app-us1.stannp.com/login
- type: TermsOfService
  url: https://www.stannp.com/us/terms-of-service
- type: PrivacyPolicy
  url: https://www.stannp.com/us/privacy-policy
- type: RateLimits
  url: rate-limits/stannp-rate-limits.yml
- type: FinOps
  url: finops/stannp-finops.yml
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
x-enrichment:
  date: '2026-08-13'
  status: enriched
  artifacts_added: 25
  pass: local-v1

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