BlockChalk website screenshot

BlockChalk

BlockChalk was a location-based neighborhood messaging service founded in 2009 by Stephen Hood, the former product lead for Delicious, and Dave Baggeroer of the Stanford Institute of Design. Users with GPS-enabled smartphones left short public messages called "chalks" pinned to a specific geographic point, and read the chalks other people had left on their block, so neighbors could ask, answer, praise, gripe, report potholes and lost pets, announce garage sales and organize locally. The company raised $1M in seed financing in May 2010 from Joshua Schachter, Battery Ventures, Founder Collective, Harrison Metal, Mitch Kapor, Josh Stylman, Tom McInerney and David Liu. BlockChalk published a small read-only public API on its developer page, offering XML, JSON and RSS interfaces that returned nearby chalks for a supplied latitude and longitude, later joined by a versioned GeoRSS endpoint. The product and the company are retired: blockchalk.com holds an active domain registration but its delegated nameservers no longer resolve, and no BlockChalk host answers on the public internet. This profile preserves the historical API surface as documentation.

BlockChalk publishes 1 API on the APIs.io network: chalks API. Tagged areas include Company, Location, Geolocation, Social, and Messaging.

BlockChalk’s developer surface includes documentation, API reference, and 4 more developer resources.

🌐 Visit website 📡 Source on GitHub
25.3/100 emerging ▬ flat Agent 21/100 agent aware Full breakdown ↓
scored 2026-07-27 · rubric v0.5
AccessOpen
1 APIs
CompanyLocationGeolocationSocialMessagingLocalNeighborhoodMobileRetired

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-07-27 · rubric v0.5
Composite quality — 25.3/100 · emerging
Contract Quality 13.1 / 25
Developer Ergonomics 3.0 / 20
Commercial Clarity 0.0 / 20
Operational Transparency 0.0 / 13
Governance 0.0 / 12
Discoverability 9.3 / 10
Agent readiness — 21/100 · agent aware
Machine-Readable Contract 18 / 18
Agentic Access Contract 0 / 15
MCP Server 0 / 12
Machine-Readable Auth 0 / 10
Idempotency 0 / 9
Stable Error Semantics 0 / 8
Request/Response Examples 0 / 7
Rate-Limit Signaling 0 / 7
Typed Event Surface 0 / 6
Agent Skills 0 / 5
Well-Known Catalog 4 / 4
Consent & Bot Identity 0 / 3
Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. This rating is computed from github.com/api-evangelist/blockchalk: open an issue to ask a question, or submit a pull request to add artifacts. Want it done for you? Prioritized profiling — $2,500 →

APIs 1

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

BlockChalk chalks API

Location-pinned neighborhood messages.

Security Posture 2

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

Blockchalk Authentication

0 schemes

SECURITY

Blockchalk Domain Security

HSTS

SECURITY

Resources

Documentation 2

Reference material describing how the API behaves

Documentation
Documentation
 APIReference
APIReference

Agent Surfaces 2

MCP servers, agent skills, and machine-readable catalogs

WellKnown
WellKnown
 LLMsTxt
LLMsTxt

Build 1

SDKs, sample code, and the tooling you integrate with

Packages
Packages

Access & Security 1

Authentication, authorization, and security posture

DomainSecurity
DomainSecurity

Source (apis.yml)

apis.yml Raw ↑ 
aid: blockchalk
accessModel:
  pricing: unknown
  onboarding: open
  trial: false
  try_now: false
  public: true
  label: Open access
  confidence: medium
  source:
  - authentication
  generated: '2026-07-22'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/blockchalk.png
name: BlockChalk
description: 'BlockChalk was a location-based neighborhood messaging service founded in 2009 by Stephen Hood, the former product
  lead for Delicious, and Dave Baggeroer of the Stanford Institute of Design. Users with GPS-enabled smartphones left short
  public messages called "chalks" pinned to a specific geographic point, and read the chalks other people had left on their
  block, so neighbors could ask, answer, praise, gripe, report potholes and lost pets, announce garage sales and organize
  locally. The company raised $1M in seed financing in May 2010 from Joshua Schachter, Battery Ventures, Founder Collective,
  Harrison Metal, Mitch Kapor, Josh Stylman, Tom McInerney and David Liu. BlockChalk published a small read-only public API
  on its developer page, offering XML, JSON and RSS interfaces that returned nearby chalks for a supplied latitude and longitude,
  later joined by a versioned GeoRSS endpoint. The product and the company are retired: blockchalk.com holds an active domain
  registration but its delegated nameservers no longer resolve, and no BlockChalk host answers on the public internet. This
  profile preserves the historical API surface as documentation.'
url: https://raw.githubusercontent.com/api-evangelist/blockchalk/refs/heads/main/apis.yml
x-type: company
x-source: vc-portfolio
x-backed-by:
- battery-ventures
x-tier: stub
x-tier-reason: portfolio-lead
x-status: retired
specificationVersion: '0.20'
created: '2026-07-17'
modified: '2026-07-20'
tags:
- Company
- Location
- Geolocation
- Social
- Messaging
- Local
- Neighborhood
- Mobile
- Retired
apis:
- aid: blockchalk:blockchalk-chalks-api
  name: BlockChalk chalks API
  description: Location-pinned neighborhood messages.
  humanURL: http://web.archive.org/web/20090810213933/http://blockchalk.com/developers
  baseURL: http://blockchalk.com/api
  tags:
  - chalks
  properties:
  - type: OpenAPI
    url: openapi/blockchalk-chalks-api-openapi.yml
  - type: Examples
    url: examples/blockchalk-chalks-v0.6-georss-san-francisco.xml
  - type: Authentication
    url: authentication/blockchalk-authentication.yml
  - type: Conventions
    url: conventions/blockchalk-conventions.yml
  - type: DataModel
    url: data-model/blockchalk-data-model.yml
  - type: Lifecycle
    url: lifecycle/blockchalk-lifecycle.yml
  - type: Conformance
    url: conformance/blockchalk-conformance.yml
common:
- type: Documentation
  url: http://web.archive.org/web/20090810213933/http://blockchalk.com/developers
- type: APIReference
  url: http://web.archive.org/web/20090810213933/http://blockchalk.com/developers
- type: Packages
  url: packages/blockchalk-packages.yml
- type: WellKnown
  url: well-known/blockchalk-well-known.yml
- type: DomainSecurity
  url: security/blockchalk-domain-security.yml
- type: LLMsTxt
  url: llms/blockchalk-llms.txt
x-enrichment:
  date: '2026-07-20'
  status: enriched
  artifacts_added: 13
  pass: local-v1
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io