Rinci - Language-neutral metadata for your code entities




This document describes version 1.1.103 of Rinci (from Perl distribution Rinci), released on 2022-10-21.


This document describes Rinci, a set of extensible, language-neutral metadata specifications for your code (functions/methods, variables, packages, classes, and so on). Rinci allows various helper tools, from code generator to web middleware to documentation generator to other protocols, to act on your code, making your life easier as a programmer. Rinci also allows better interoperability between programming languages. Rinci is geared towards dynamic scripting languages like Perl, Python, Ruby, PHP, JavaScript, but is not limited to those languages.


The 1.1 series does not guarantee full backward compatibility between revisions, so caveat implementor. However, major incompatibility will bump the version to 1.2 or 2.0.


The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

Rinci is a set of specifications of metadata for your code entities. Each different type of code entity, like function/method, variable, namespace, etc, has its own metadata specification.

Metadata is a defhash (see DefHash). Each specification will specify what properties should be supported. So the Rinci::function specification will describe metadata for functions/methods, Rinci::package will describe metadata for namespace/package, and so on.

Rinci defines properties pertaining to documentation (like summary, description, examples, links), function argument and return value validation (args and result), dependencies (deps), standardized feature description (features), also a few conventions/protocols for doing stuffs like undo (others like callback/progress report will follow). Basically anything that can describe the code entity. The specification is extensible: you can define more properties, or more deps, or more features.

Since defhash can contain keys that are ignored (those that start with underscore, _), extra information can be put here.


By adding Rinci metadata to your code, you can write/use tools to do various things to your program. Rinci is designed with code generation and function wrapping in mind. At the time of this writing, in Perl there exists several tools (mostly modules under Perinci namespace) to do the following:

  • Perinci::Sub::Wrapper

    Wrap functions with a single generated function that can do the following: validate input (using information from the args property), validate return value (the result property), add execution time-limiting (timeout), add automatic retries (retry), interactive confirmation, logging, and more.

  • Perinci::Exporter, Exporter::Rinci

    More convenient replacements/wrappers for Exporter or Sub::Exporter if your functions are equipped with Rinci metadata. Automatically provide export tags (using information in the tags property). Automatically wrap functions using Perinci::Sub::Wrapper when exporting (Perinci::Exporter).

  • Perinci::To::* modules

    Convert metadata to various other documents, for example Perinci::To::POD to generate documentation.

  • Perinci::CmdLine (several flavors: Perinci::CmdLine::Classic, Perinci::CmdLine::Lite, Perinci::CmdLine::Inline)

    Riap command-line client. Call local/remote functions. Automatically convert command-line options/arguments to function arguments. Generate help/usage message (for --help). Check dependencies (e.g. you can specify that in order to run your functions, you need some executables/other functions to exist, an environment variable being set, and so on), perform bash shell completion (using Perinci::Sub::Complete).

  • Perinci::Access::HTTP::Server

    A PSGI application (a set of PSGI middlewares, really) to serve metadata and function call requests over HTTP, according to the Riap::HTTP protocol.

  • Serabi

    An alternative for Perinci::Access::HTTP::Server for REST-style service.

  • Perinci::Use

    Use remote packages and import their functions/variables transparently like you would use local Perl modules. The remote server can be any Riap-compliant service, even when implemented in other languages.

  • Perinci::Sub::Gen::*

    Since Rinci metadata are just normal data structure, they can be easily generated. The Perinci::Sub::Gen::* Perl modules can generate functions as well as their metadata, for example to access table data (like from a regular array or from a SQL database).

More tools will be written in the future.


Some features offered by Rinci (or Rinci tools) are undoubtedly already offered by your language or existing language libraries. For example, for documentation Perl already has POD and Python has docstrings. There are numerous libraries for argument validation in every language. Python has decorators that can be used to implement various features like argument validation and logging. Perl has subroutine attributes to stick additional metadata to your subroutines and variables. And so on.

The benefits that Rinci offer include richer metadata, language neutrality, extensibility, and manipulability.

Richer metadata. Rinci strives to provide enough metadata for tools to do various useful things. For example, the description and summary properties support translations. Argument specification is pretty rich, with a quite powerful and flexible schema language.

Language neutrality. You can share metadata between languages, including documentation and rules for argument validation. Perl 6 allows very powerful argument validation, for example, but it is language-specific. With Rinci you can easily share validation rules and generate validators in Perl and JavaScript (and other target languages).

Manipulability. Being a normal data structure, your Rinci metadata is easier to manipulate (clone, merge, modify, export, what have you) as well as access (from your language and others). Perl's POD documentation is not accessible from the language (but Perl 6's Pod and Python docstrings are, and there are certainly tools to parse POD). On the other hand, Python docstrings are attached in the same file with the function, while with Rinci you can choose to separate the metadata into another file more easily.

Other things to consider. If you stack multiple decorators in Python, for example, it usually results in wrapping your Python function multiple times, which can add overhead. A single wrapper like Perinci::Sub::Wrapper, on the other hand, uses a single level of wrapping to minimize subroutine call overhead.

Working together. There is no reason why Rinci metadata has to compete against existing features from language/libraries. A code generator for Rinci metadata can generate code that utilize those features. For example, the timeout property can be implemented in Python using decorator, if you want. Rinci basically just provides a way for you to express desired properties/constraints/behaviours, separate from the implementation. A tool is free to implement those properties using whatever technique is appropriate.


Note: Examples are usually written in Perl, but this does not mean they only apply to a particular language.


Code entities, or just entities for short, are elements in your code that can be given metadata. Currently supported entities are function/method, namespace/package, and variable. Other entities planned to be supported: class, object, library, application.

Specification common to all metadata

This section describes specification common to all kinds of Rinci metadata.

Where to put the metadata. The specification does not specify where to put metadata in: it might be put alongside the code, separated in another source code, encoded in YAML/JSON, put in database, or whatever. It is up to the tools/implementations to provide the mechanism. If you use Perinci in Perl, there is a great deal of flexibility, you basically can do all of the above, even split the metadata in several files. See its documentation for more details.

Common properties. Below are properties common to all metadata:

Property: v => FLOAT (required)

From DefHash. Declare specification version. This property is required. It should have the value of 1.1. If v is not specified, it is assumed to be 1.0 and metadata is assumed to be the old, Sub::Spec 1.0.x metadata.


 v => 1.1

Property: entity_v => STR

Specify entity version (like package or function version). This is version as in software implementation version, not to be confused with v which is the metadata specification version (1.1).


 entity_v => 0.24

In Perl, modules usually put version numbers in package variable called $VERSION. If not set, tools like Perinci::Access::Perl automatically fills this property from that variable, to relieve authors from manually setting this property value.

Property: default_lang => STR

From DefHash. Specify default language used in the text properties like summary and description. Default is 'en_US'.

To specify translation texts in other languages, you can use PROPERTY.alt.lang.CODE, e.g.:

 summary => "Perform the foo ritual",
 "summary.alt.lang.id_ID" => "Laksanakan ritual foo",

Property: name => STR

From DefHash. The name of the entity. Useful when aliasing entity (and reusing the metadata) and wanting to find out the canonical/original entity.


 name => 'foo'
 name => '$var'  # only in languages where variables have prefix

Property: summary => STR

From DefHash. A one-line summary. It should be plain text without any markup. Please limit to around 72 characters.


 # in variable metadata for $Answer
 summary => 'The answer to the question: what is the meaning of life'

 # in function metadata foo
 summary => 'Perform the foo ritual',

For variable metadata, it should describe what the variable contain. You do not need to say "Contains ..." or "A variable that ..." since that is redundant; just say directly the content of the variable (noun). You also do not need to say what kinds of values the variable should contain, like "An integer, answer to the ..." or "..., should be between 1..100" since that should go to the schema property.

For function metadata, it should describe what the function does. Suggestion: use active, bare infinitive verb like in the example (not "Performs ..."). Avoid preamble like "This function ..." or "Function to ..." since that is redundant. Also avoid describing the arguments and its values like "..., accepts a single integer argument" as that should go to the args property.

To specify translations in other language, use the summary.alt.lang.CODE. Or change the default_lang property. Examples:

 # default language is 'en_US'
 summary => 'Perform the foo ritual',
 "summary.alt.lang.id_ID" => 'Laksanakan ritual foo',

 # change default language to id_ID, so all summaries are in Indonesian, except
 # when explicitly set otherwise
 default_lang => 'id_ID',
 summary => 'Laksanakan ritual foo',
 "summary.alt.lang.en_US" => 'Perform the foo ritual',

Property: tags => ARRAY OF (STR OR HASH)

From DefHash. A list of tags, useful for categorization. Can also be used by tools, e.g. Perinci::Exporter in Perl uses the tags property of the function metadata as export tags.

Tag can be a simple string or a tag metadata hash.


 # tag a function as beta
 tags => ['beta']

 # the second tag is a detailed metadata
 tags => ['beta',
              name    => 'category:filtering',
              summary => 'Filtering',
              "summary.alt.lang.id_ID" => 'Penyaringan',

Property: description => STR

From DefHash. A longer description text. The text should be in marked up in format specified by text_markup and is suggested to be formatted to 78 columns.

To avoid redundancy, you should mentioning things that are already expressed as properties, for example: return value of function (specify it in result property instead), arguments that the function accepts (args), examples (examples), function's features (features) and dependencies/requirements (deps).

For function, description should probably contain a more detailed description of what the function does (steps, algorithm used, effects and other things of note).


     name => 'foo',
     summary => 'Perform the foo ritual',
     description => <<EOT,

 Foo ritual can be performed by humans or machines. This program will perform a
 machine-based ritual using [the best available

 Note that you still have to perform foo ritual manually from time to time, just
 to be safe.


Like in summary, to specify translations in other language, use the description.alt.lang.CODE property.

List to related entities or resources. Can be used to generate a SEE ALSO and/or LINKS sections in documentation. Each link is a defhash with the following keys:

  • url => STR (required)

    URI is used as a common syntax to refer to resources. If URI scheme is not specified, tools can assume that it is a riap URI (see Riap).

  • caption => STR

    From DefHash. A short plaintext title for the link.

  • description => STR

    From DefHash. A longer marked up text description for the link. Suggested to be formatted to 76 columns.

  • tags => ARRAY OF (STR OR HASH)

    From DefHash. Can be used to categorize or select links. For generating SEE ALSO sections, use the tag 'see'.


 # links in the Bar::foo function metadata
 links => [
         url     => "",
         caption => "Article describing foo using Bar algorithm",
         url     => "../Bar2/",
         caption => "Another implementation of the Bar algorithm",
         tags    => ['see'],

Property: x => ANY

From DefHash. This property is used to store extended (application-specific) attributes, much like the X- prefix in HTTP or email headers. This property can be used as an alternative to using underscore prefix (e.g. _foo). Some processing tools strip properties/attributes that begin with underscores, so to pass extended metadata around, it might be more convenient to use the x property.

It is recommended that you put an application prefix.


 "" => "some value",

Another example:

 "x.dux.strip_newlines" => 0,

Entity-specific specifications

Each entity-specific specification is described on a separate subdocument. Currently these specifications are defined:

These specifications are planned or considered, but not yet defined:


What does Rinci mean?

Rinci is taken from Indonesian word perincian or rincian, meaning: specification, detail.

Why use Sah for data schema?

Sah is a flexible and extensible schema language, while still not being language-specific, making it easy for code generator tools to generate validator code in various target languages (Perl, Ruby, etc).


Please visit the project's homepage at


Source repository is at



Sah schema language, Sah


.NET attributes,

Python Decorators, ,



Below is the general history of the project and major changes to the specifications. For more detailed changes between releases, see the Changes file in the distribution.

1.1 (Jan 2012)

To clearly separate specification from implementation, rename specification from Sub::Spec to Rinci (the namespace Perinci is now used for the Perl implementation). Support code entities other than functions/methods. Bump specification version from 1.0 to 1.1 due to several incompatibilities like changed args and result properties, terminologies, defaults. Versioning property (v) now required.

1.0 (Aug 2011)

First release version of Sub::Spec.

0.x (Feb-Aug 2011)

Series of Sub::Spec drafts.

Spanel project (2009-2010)

I started using some metadata for API functions, calling them spec and putting them in %spec instead of in POD, so I can list and grab all the summaries easily as a single dump for API catalog (instead of having to parse POD from my source code files). Later on I kept adding more and more stuffs to this, from argument specification, requirements, and so on.


perlancar <>


To contribute, you can send patches by email/via RT, or send pull requests on GitHub.

Most of the time, you don't need to build the distribution yourself. You can simply modify the code, then test via:

 % prove -l

If you want to build the distribution (e.g. to try to install it locally on your system), you can install Dist::Zilla, Dist::Zilla::PluginBundle::Author::PERLANCAR, Pod::Weaver::PluginBundle::Author::PERLANCAR, and sometimes one or two other Dist::Zilla- and/or Pod::Weaver plugins. Any additional steps required beyond that are considered a bug and can be reported to me.


This software is copyright (c) 2022, 2021, 2020, 2019, 2018, 2017, 2016, 2015, 2014, 2013, 2012 by perlancar <>.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.


Please report any bugs or feature requests on the bugtracker website

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.