application programming interface
Enable an agent to recognise an application programming interface, assess its contract and operational state, and determine which programmatic interactions are supported and permitted.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
recalled by Codex without web access - no source was read
Researched by: Codex
Purpose and description
Enable an agent to recognise an application programming interface, assess its contract and operational state, and determine which programmatic interactions are supported and permitted.
An application programming interface (API) is a specified set of operations, data types and interaction rules through which software components access functionality or exchange information without requiring knowledge of one another's internal implementation.
It can be Discover exposed capabilities and select an operation that matches a task.; Construct and validate calls or messages against the applicable contract.; Assess authorization and expected side effects before invoking an operation.; Invoke permitted operations and interpret results, errors or emitted events.; Choose retry, cancellation and recovery actions from documented guarantees.; Compare contract versions and identify required consumer migrations..
Distinguishing features
Exposes operations or interactions intended for consumption by software; a human-facing screen alone does not establish an API.
Defines how consumers request or receive capabilities and what those interactions mean; a data format alone is insufficient.
Can retain the same contract across different implementations or deployments, so a server address or running process does not identify the whole API.
May operate through local function calls, system calls or message exchange; network access and HTTP are not required.
Is the exposed interface rather than merely its documentation, SDK wrapper or underlying transport protocol.
Scope
+ Exposed operations, callable symbols, messages, events and associated semantics
+ Input and output types, validation rules, errors and behavioural guarantees
+ Invocation mechanisms, bindings and interaction patterns
+ Access requirements, permissions and constraints on side effects
+ Observable interface state, compatibility and lifecycle
- Internal algorithms and architecture of implementing software
- Complete business models and records accessed through the interface
- Hosting infrastructure and physical equipment
- Human-facing user interfaces
- Individual requests, responses and execution traces as independent records
- Complete SDK products and application binary interfaces, except where they constrain API use
Characteristics
- Interface form
- Library API, operating-system API, remote-service API, event interface, other documented form Determines how a consumer discovers, binds to and invokes the interface.
- Contract authority
- Links to authoritative specifications, declarations, documentation and responsible maintainers Identifies which evidence governs interpretation when descriptions or implementations disagree.
- Interaction pattern
- Synchronous call, asynchronous request, callback, publish-subscribe, stream; combinations allowed Determines completion handling, correlation and consumer control flow.
- Operation effect
- Read, create, update, delete, execute, subscribe or mixed; assessed per operation Makes consequential interactions distinguishable from observation.
- Access context
- Required identity, permission scopes, process privileges, tenant and resource constraints Determines whether a particular consumer may perform a particular operation.
- Contract version and compatibility
- Version identifier or unversioned; compatible, conditionally compatible, breaking or unassessed relative to a named baseline Prevents assuming that an existing consumer remains valid after a change.
- Invocation limits
- Where applicable: requests per stated interval, concurrent calls, bytes per message and seconds per timeout; include scope and evidence Constrains call planning, batching and resource consumption.
- Observed usability
- Available, degraded, unavailable or unknown for a specified implementation, consumer context and observation time Separates a valid interface contract from whether an agent can currently use a particular realization.
- Lifecycle stage
- Experimental, supported, deprecated, retired or unknown according to the provider Guides adoption, migration and continued reliance.
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 18 findings · 29 questions.
Interface identity and contract Establishes which API is being described and which declarations govern its exposed capabilities.
An agent must distinguish an interface from similarly named products, wrappers and deployments before relying on its contract.
Identity and boundary
Locates the software interaction boundary and relates it to providers, consumers and realizations.
API boundary
Record the interface's identity, intended consumers and separation from its implementing software, SDKs and deployment locations.
- Which software capabilities and consumer interactions define this API's boundary? definition
- Which named SDKs, services, bindings or deployments implement or wrap this API rather than constitute separate API contracts? boundary
Contract authority and surface
Identifies authoritative descriptions and the operations or messages they expose.
Authoritative capability inventory
Record exposed functions, methods, endpoints, events or messages and the evidence defining their supported behaviour.
- Which specification, source declarations or provider documentation govern this contract, and for which version? provenance
- Which callable operations or exchanged messages are supported, and which observed behaviours are undocumented? definition
Inputs, outputs and effects Describes what an interaction accepts, returns and changes.
A syntactically valid invocation can still be semantically wrong or produce unintended changes.
Value contracts
Captures the meaning and admissible forms of arguments, payloads and results.
Types, validation and representation
Record required values, types, units, encodings, nullability, defaults and constraints for each interaction.
- What types, required fields, units and validation rules apply to each operation's inputs and outputs? definition
- How do omission, null values, default values and unknown fields affect interpretation? boundary
Behavioural contracts
Captures operation meaning beyond value shapes.
Preconditions, effects and guarantees
Record prerequisites, observable changes, result meaning and any atomicity, consistency or idempotency guarantees.
- What must hold before invocation, and what results or state changes does successful completion guarantee? definition
- Which operations cause external effects, and under what documented conditions can they be repeated or reversed? action
Binding and execution Describes how consumers reach the interface and manage an interaction through completion.
Correct API use depends on binding, sequencing and lifetime rules that cannot be inferred from operation names.
Binding and addressing
Captures the mechanism for locating and connecting to the intended interface realization.
Consumer binding requirements
Record applicable imports, symbol resolution, endpoint discovery, protocol negotiation and runtime requirements.
- How does a consumer locate and bind to this API in each supported interface form? action
- Which language, runtime, transport or platform requirements constrain a supported binding? boundary
Interaction lifecycle
Captures call sequencing, completion signals and ownership of resources created during interaction.
Completion, ordering and resource lifetime
Record synchronous or asynchronous completion, event correlation, ordering, cancellation and cleanup obligations where applicable.
- How does the consumer distinguish acceptance, progress and completion, and correlate subsequent results or events? definition
- What sequencing, concurrency, cancellation and resource-release rules must the consumer follow? action
Access and operational recovery Establishes who may interact, under which limits, and how failures should be handled.
An agent needs explicit permission and recovery evidence to avoid unauthorized actions, duplicate effects and uncontrolled retries.
Authorization context
Captures the identity and privilege conditions applicable to an invocation.
Effective operation permissions
Record authentication mechanisms and operation-specific permissions, including process privileges or tenant boundaries where relevant.
- What identity or execution context is required, and how is its authority established? definition
- Is the proposed operation permitted for this consumer, target resource and tenant or process context? action
Limits, errors and recovery
Captures operational constraints and the meaning of unsuccessful or ambiguous outcomes.
Failure-aware invocation
Record error forms, timeout meaning, applicable quotas and evidence supporting retry or reconciliation.
- What documented or measured call, payload, concurrency and timing limits apply, with what units and scope? measurement
- After an error, timeout or lost response, how can an agent determine whether effects occurred and whether retrying is safe? action
- Which observations establish current usability for the relevant implementation and consumer context? provenance
Compatibility and evolution Tracks supported contract changes and the evidence that consumers can continue operating.
An API can remain reachable while changes to values, behaviour or support policy invalidate existing consumers.
Version selection and compatibility
Captures how versions are selected and which changes preserve consumer expectations.
Consumer compatibility boundary
Record version selection mechanisms and compatibility assessments against a named contract and consumer baseline.
- How is the applicable contract version selected or identified for an invocation? definition
- Which changes to signatures, payloads, errors or behaviour would break the specified consumer's expectations? boundary
Support and conformance evidence
Connects lifecycle declarations and observed implementation behaviour to adoption and migration decisions.
Support status and migration readiness
Record provider lifecycle notices, implementation deviations and evidence needed to adopt or migrate a consumer.
- Which dated provider notices establish support, deprecation or retirement, and what replacement is identified? provenance
- What contract checks and consumer changes are needed before adopting this implementation or migrating to its successor? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Check these first
Recalled without web access and unsourced; every item is a lead to verify.
- This describes the general software-interface sense; the supplied PHY.OBJ classification should be reviewed because an API is not ordinarily a physical object.
- The listed kinds overlap, and the standards apply to particular API families rather than to every API.
- Latency, throughput, availability and rate limits characterize particular API implementations or services; no meaningful universal typical ranges apply.
- Which of these check these first hold for the sense of application programming interface this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Library APIs
- Operating-system APIs
- Remote procedure call APIs
- HTTP-based web APIs
- Database access APIs
- Graphics and compute APIs
- Which of these kinds and varieties hold for the sense of application programming interface this model covers, and on what evidence? provenance
Identifiers and schemes
Recalled without web access and unsourced; every item is a lead to verify.
- URI - scheme:[//authority]path[?query][#fragment] - Network APIs may use URIs to identify resources or endpoints; a URI is not a universal identifier for an API specification.
- Which of these identifiers and schemes hold for the sense of application programming interface this model covers, and on what evidence? provenance
Standards and regulation
Recalled without web access and unsourced; every item is a lead to verify.
- OpenAPI Specification - OpenAPI Initiative; a description format for HTTP APIs.
- POSIX, IEEE Std 1003.1 - IEEE; standardizes operating-system interfaces, among other facilities.
- HTTP Semantics, RFC 9110 - IETF; defines protocol semantics used by HTTP APIs.
- OAuth 2.0 Authorization Framework, RFC 6749 - IETF; defines delegated authorization commonly used to control API access.
- Web IDL - WHATWG; defines an interface description language used to specify web-platform APIs.
- Which of these standards and regulation hold for the sense of application programming interface this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Calling reusable functions supplied by software libraries.
- Accessing operating-system services such as files, processes and networking.
- Connecting applications to remote services for payments, mapping or messaging.
- Allowing plugins and extensions to interact with a host application.
- Providing programmatic access to databases, graphics processors and other computing facilities.
- Which of these real-world use hold for the sense of application programming interface this model covers, and on what evidence? provenance
Failure modes and hazards
Recalled without web access and unsourced; every item is a lead to verify.
- Incompatible interface changes break existing clients.
- Ambiguous contracts or inconsistent error handling lead to incorrect integration.
- Missing authentication or inadequate authorization exposes data or privileged operations.
- Timeouts and retries can duplicate side effects unless operations provide suitable idempotency guarantees.
- Unbounded requests, excessive resource consumption or dependency outages degrade service availability.
- Which of these failure modes and hazards hold for the sense of application programming interface this model covers, and on what evidence? provenance
Regional variation
Recalled without web access and unsourced; every item is a lead to verify.
- The core concept is not region-specific, but APIs processing personal data may face jurisdiction-specific requirements concerning access, retention and cross-border transfer.
- Which of these regional variation hold for the sense of application programming interface this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Recalled without web access and unsourced; every item is a lead to verify.
- implementation - The API specifies externally available interactions; the implementation contains the code and mechanisms that perform them.
- communication protocol - A protocol defines communication rules between participants; an API defines a software-facing interface and may operate locally or use a protocol remotely.
- application binary interface - An ABI specifies binary-level conventions such as calling conventions and data layout; an API generally specifies interactions at the programming or service-contract level.
- software development kit - An SDK packages development tools and supporting materials and may include libraries implementing or accessing an API.
- web service - A web service supplies functionality over a network; its API describes how software accesses that functionality.
- user interface - A user interface primarily supports human interaction; an API supports interaction by software.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of application programming interface this model covers, and on what evidence? provenance
What the second pass must settle
- Does PHY / PHY.OBJ intentionally classify the API as a realized software boundary, or should the registry classify its contract in another plane?
- Which existing Vercy world model, if any, already owns the API concept and should serve as its single source of truth?
- Should this registry entry encompass local library APIs, operating-system APIs and remote interfaces equally, and where should its boundary with an application binary interface fall?
- Which authoritative sources should establish the researched definition and terminology for this broad API model?
- How should later publications distinguish contractual guarantees from provider claims and observations of a particular implementation?