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 contract indexed on the APIs.io network: Chalks API. Tagged areas include Company, Location, Geolocation, Social, and Messaging.

The BlockChalk catalog on APIs.io includes 1 Spectral governance ruleset.

BlockChalk’s developer surface includes documentation, API reference, and 6 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

0.0/100 minimal ▬ flat Agent 0/100 human only library Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

AccessOpen

1 published contract

Company Location Geolocation Social Messaging Local Neighborhood Mobile Retired

Kin Score

Kin Score How this is scored →
scored 2026-11-06 · rubric v0.27.0

Composite quality — 0.0/100 · minimal

Contract Quality 0.0 / 21

Developer Ergonomics 0.0 / 17

Access Clarity 0.0 / 17

Operational Transparency 0.0 / 11

Contract Governance 0.0 / 10

Discoverability 0.0 / 9

Regulatory Posture 2.5 / 15

Agent readiness — 0/100 · human only

Machine-Readable Contract 18 / 18

Agentic Access Contract 0 / 10

Documented Reversibility 6 / 6

MCP Server 0 / 12

Machine-Readable Auth 10 / 10

Idempotency 9 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 7 / 7

Rate-Limit Signaling 0 / 7

Typed Event Surface 0 / 6

Agent Skills 0 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 4 / 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

MCP Tool Quality 6 / 6

Regulatory Posture applies to this provider. Its tags matched the Horizontal (data, software, accessibility, platform) 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 does not apply to this provider. The published contracts declare no write operations, and a read-only API cannot create-or-update. The facet is excluded from this provider's denominator entirely — not scored zero. A reference or data API is not deficient for being unable to upsert.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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It updates itself when the score changes. Paste this where you link to your API docs:

<a href="https://apis.io/providers/blockchalk/"><img src="https://apis.io/badge/blockchalk/card.svg" alt="BlockChalk on APIs.io — Kin Score by API Evangelist"></a>

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Agent readiness — checks not met, largest first (exact, from this profile):

MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship
Agentic Access Contract +10 pts — agentic_access artifact present (x-agentic-access), graded by author
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0
Rate-Limit Signaling +7 pts — OpenAPI responses document X-RateLimit-* / RateLimit headers (verified), else a rate_limits artifact or RateLimits link (documented)
Registration Without a Human +6 pts — a `registration_endpoint` in the served RFC 8414 / OIDC discovery document

7 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Contract Quality scores 0.0 — up to +25.0 composite points
Developer Ergonomics scores 0.0 — up to +20.0 composite points
Access Clarity scores 0.0 — up to +20.0 composite points

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

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 the provider profile at artifacts.apis.io/blockchalk/apis.yml: open an issue on github.com/api-evangelist/blockchalk to ask a question or point us at an artifact you publish. 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
Mobile SDK Publishers (Play SDK Index, CocoaPods, ADA certification)	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.

Standards implemented 1

Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.

OpenAPI

measured — observed by APIs.io (published)

APIs 1

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

BlockChalk Chalks API

Location-pinned neighborhood messages.

Open Collections 1

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

BlockChalk API (historical) chalks API

OPEN COLLECTION

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

BlockChalk API Rules

37 rules · 35 errors 1 warnings 1 info

SPECTRAL

OpenAPI Overlays 1

Overlays applied on top of this provider's contracts. Each card says who wrote it: a document the provider publishes, or one API Evangelist derived or generated.

Blockchalk Chalks Overlay

5 actions · update · blockchalk-chalks-openapi.yml

DERIVED

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

Company 1

The organization behind the API

Website

Website

Other 1

Properties that don't map to a standard resource type

Overlay

Overlay

Source (apis.yml)

aid: blockchalk
deliveryModel:
  model: library
  open_source: false
  commercial: false
  callable_host: false
  label: Library · distributed through package registries, no callable service
  confidence: low
  source:
  - openapi
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: unknown
  onboarding: open
  trial: false
  try_now: false
  public: true
  gated: none
  gated_source:
  - onboarding
  label: Open access
  confidence: low
  source:
  - authentication
  - security
  generated: '2026-11-06'
  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: '0.23'
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: Website
  url: https://www.archive.org/
- type: Overlay
  url: overlays/blockchalk-chalks-overlay.yaml
- 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

BlockChalk API — frequently asked questions

Does BlockChalk have an API?

Yes. APIs.io lists 1 API from BlockChalk, including BlockChalk Chalks API.

Is there an OpenAPI specification for the BlockChalk API?

Yes. APIs.io indexes 1 OpenAPI specification for BlockChalk, each linked for download from this page.

How do I authenticate with the BlockChalk API?

BlockChalk uses bearer-token authentication (0 schemes). The details are profiled on APIs.io as Blockchalk Authentication.

Is the BlockChalk API ready for AI agents?

BlockChalk has a Kin Score of 0.0 out of 100 (minimal) and an Agent Readiness score of 0.0 (human-only), scored by API Evangelist on 2026-11-06.

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