Accept Language Parser MCP. Correctly route traffic based on weighted language preferences
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The `parse_accept_language` tool takes raw HTTP `Accept-Language` headers (e.g., `en-US,pt-BR;q=0.9,fr;q=0.8`) and converts them into a deterministic, prioritized list of language preferences.
It correctly interprets quality weights (q-factors) according to RFC 7231, ensuring the user's actual preferred language is always identified first.
This is essential for global routing and internationalization agents.
What your AI agents can do
Parse accept language
Takes a raw Accept-Language header and returns a sorted list of language preferences with their quality weights.
Input a raw Accept-Language header string and get a list of languages sorted by preference, starting with the highest quality weight.
Reads the numeric quality factor (q-value) from each language tag in the header, providing a machine-readable weight for sorting.
Automatically flags the single most preferred language based on the header's structure (usually q=1).
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Accept Language Parser MCP Server: 1 Tool
This tool allows you to parse raw HTTP Accept-Language headers and return a priority-ordered list of languages with their quality weights.
019e385fparse accept language
Takes a raw Accept-Language header and returns a sorted list of language preferences with their quality weights.
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What you can do with this MCP connector
Listen up. You're dealing with HTTP Accept-Language headers, right? They look like a mess: en-US,pt-BR;q=0.9,fr;q=0.8. You need to know exactly what language the user wants, and you need it fast. The parse_accept_language tool takes that raw, messy header string and spits out a clean, sorted list of language preferences. It follows RFC 7231 rules, period.
You'll never have to write custom logic for quality weights again.
Determine Language Priority
Give it a raw Accept-Language header string, and it'll give you a list of languages sorted by preference, starting with the highest quality weight. It figures out the order for you. You'll always know the user's top choice first.
Extract Quality Weights
It reads the numeric quality factor, or 'q-value', from every language tag in the header. This gives you a machine-readable weight for sorting, so you can process the data programmatically. You get the weight for each language tag.
Identify Preferred Language
It automatically flags the single most preferred language based on how the header is structured—usually when the quality weight is set to q=1. This makes finding the top choice dead simple.
If you run it with Accept-Language: en-US,pt-BR;q=0.9,fr;q=0.8, the output shows the preference order: en-US (q=1) > pt-BR (q=0.9) > fr (q=0.8). The list is ordered by quality weight, putting the highest preference first. It handles global routing and internationalization agents that need reliable language detection. You're gonna get accurate data every time.
How Accept Language Parser MCP Works
- 1 Pass the raw
Accept-Languageheader value (e.g., "en-US,pt-BR;q=0.9,fr;q=0.8") to theparse_accept_languagetool. - 2 The tool processes the string, calculating and applying the quality weights (q-factors) according to HTTP standards.
- 3 You receive a structured list of language tags, ordered from highest to lowest preference.
The bottom line is, you don't need to write complex regex or custom logic to figure out a user's preferred language from a header; the tool handles the whole parsing process.
Who Is Accept Language Parser MCP For?
Global site architects and platform engineers need this. If your application serves content in multiple languages, you can't rely on simple fallbacks. You need to know the user's actual preferred language, weighted by how much they value it. This is for the person who gets burned by incorrect routing and lost international revenue.
Integrates the language parsing into global routing middleware to ensure users are directed to the highest-quality localized content endpoint.
Builds content delivery pipelines that must respect complex language prioritization rules beyond simple 'English first' logic.
Uses the tool to validate and debug traffic flow, ensuring that regional headers are processed correctly before hitting the application layer.
What Changes When You Connect
- Accurate Routing: Instead of guessing, the
parse_accept_languagetool provides a deterministic, weighted order of languages. Your agent always knows the user's true preference, preventing costly routing errors. - RFC Compliant: This tool adheres exactly to HTTP standard RFC 7231 rules. You don't waste time debugging custom parsing logic that breaks on edge-case language tags or quality weights.
- Handles Complexity: It manages complex headers like
en-US,pt-BR;q=0.9,fr;q=0.8instantly. You feed it the raw header, and it spits out the weighted priority list. - Single Source of Truth: Centralizes language preference logic. You stop writing and maintaining brittle, ad-hoc header parsing functions across multiple services.
- Global Scalability: Built for production environments. When your user base expands globally, the language parsing logic stays solid and compliant.
Real-World Use Cases
Directing a User to the Right Site Version
A user hits your main domain with the header zh-CN,zh;q=0.9,en;q=0.8. The agent runs parse_accept_language. The tool returns zh-CN as the top preference. The agent then routes the request to your Chinese site, ensuring the user sees the correct regional content, not just the default English version.
Validating Multi-Region Content Delivery
An i18n engineer needs to test if their staging environment correctly handles multiple language fallbacks. They run parse_accept_language on a complex header. The tool confirms the exact order (de > en-GB > ja), allowing the agent to programmatically test and validate that the content pipeline serves the correct resources in the correct sequence.
Debugging Routing Failures in Production
A global router fails sporadically, sometimes sending users to the wrong locale. The operations engineer uses parse_accept_language to capture the raw header and verify the expected language order. The tool immediately highlights where the parsing logic deviates from the HTTP standard, fixing the bug.
Building Composable Agent Pipelines
A developer is building a complex agent workflow that needs to know the client's language intent early on. They use parse_accept_language as the first step, feeding the resulting prioritized language list into subsequent tools, guaranteeing that all downstream actions are language-aware.
The Tradeoffs
Simple Comma Splitting
Just splitting the header by commas and assuming the first language is the best one. Example: en-US,pt-BR;q=0.9,fr;q=0.8 -> en-US (incorrectly ignoring q-factors).
→
Always use parse_accept_language. It respects the quality weights. It sees that even though en-US is first, the true weighted order is en-US > pt-BR > fr, giving you the accurate priority.
Hardcoding Fallbacks
Writing logic that says 'If language is unknown, default to 'en-US'.' This fails when the user is actually from a different region that just prefers a different language, like 'es-MX'.
→
Let parse_accept_language analyze the header. It provides the entire weighted list, so you can check for and route to any specific language tag (like es-MX) without assuming a default.
Manual Quality Weight Parsing
Writing custom regex to extract q=0.9 and q=0.8. This is brittle and breaks immediately if the header format changes slightly or if a new language tag is introduced.
→
Don't write the regex. Use parse_accept_language. It handles the entire standard parsing process, making your code cleaner and compliant.
When It Fits, When It Doesn't
Use this MCP Server if your application's routing or content delivery system absolutely depends on knowing the user's weighted language preference. This is critical for global platforms that must adhere to RFC 7231.
Don't use it if you simply need to check if a language is present, or if your site only supports one primary language. If you only need to check for a single tag, a simple string check works. But if you need the order or the weight, you need parse_accept_language.
If you find yourself writing logic to handle q-values or checking for the presence of specific language codes in a complex header, stop. Use this tool instead.
Independent Platform Disclaimer: Vinkius is an independent platform and is not affiliated with, endorsed by, sponsored by, verified by, or otherwise authorized by accept-language-parser. All third-party trademarks, logos, and brand names are the property of their respective owners. Their use on this website is strictly for informational purposes to identify service compatibility and interoperability.
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Available Capabilities
Dealing with complex global language headers is a constant headache.
When you build a site for a global audience, you quickly run into messy headers. The `Accept-Language` header isn't a simple list; it's a complex string that contains quality weights (`q=0.9`, `q=0.8`) and multiple regional tags. Manually parsing these—or even relying on basic comma splitting—is a recipe for broken internationalization (i18n) layers.
With the `parse_accept_language` MCP Server, you simply pass the raw header. The tool handles the complex HTTP standard logic and spits out a clean, ordered list. You get a reliable, deterministic language priority that your agent can use immediately.
Using the Accept Language Parser MCP Server
The manual steps you eliminate are the regex writing, the quality weight calculation, and the sorting logic. Instead of writing 50 lines of boilerplate code to manage RFC compliance, you call one tool function.
Your agent now handles language routing with native compliance. The language logic is moved out of your core application code and into a dedicated, tested service.
Common Questions About Accept Language Parser MCP
How does the parse_accept_language tool handle quality weights? +
The tool processes quality weights (q-factors) exactly as defined by RFC 7231. It uses these weights to calculate the true priority, ensuring the language with the highest weight is listed first, even if it's not the first language in the header.
Can I use parse_accept_language for languages other than English? +
Yes. The tool parses the standard language tags (like pt-BR or fr) regardless of the specific language. It focuses on the HTTP format, not the language content.
What format does the output of parse_accept_language have? +
The output is a structured, ordered list. It tells you the language tag and its associated quality weight, making it easy for your agent to read the preference hierarchy.
Is parse_accept_language faster than writing my own parser? +
Yes. It is built to handle the full HTTP standard efficiently, removing the risk of subtle compliance errors and improving the reliability of your routing logic.
How does the `parse_accept_language` tool handle malformed or empty HTTP headers? +
The tool handles malformed headers gracefully by returning an empty, ordered list and logging the error. You don't need to worry about strict input validation; it's built to fail safely, which is crucial when dealing with varied web traffic.
What kind of data inputs does `parse_accept_language` expect besides the raw header string? +
It expects only the raw header value (e.g., "en-US,pt-BR;q=0.9,fr;q=0.8"). It's designed to take that single string input, making it simple to integrate into any agent workflow without complex pre-processing steps.
Is the `parse_accept_language` tool compatible with non-standard language tags? +
Yes, it follows RFC 7231, meaning it correctly interprets standard and common non-standard language tags. It processes the structure and quality weights, not just the tag names, giving you reliable results even with unusual inputs.
If I pass multiple Accept-Language headers, can `parse_accept_language` process them? +
No, the tool is designed to process a single, concatenated Accept-Language header string. You must provide the full header value in one go. This focus keeps the output deterministic and prevents ambiguity in the parsing logic.
What is a quality weight (q-factor)? +
A value from 0 to 1 indicating preference. q=1 (default) is highest priority. q=0 means the language is explicitly not accepted.
Does it handle regional subtags? +
Yes. pt-BR is parsed as code=pt, region=BR. en-US as code=en, region=US. The region is separated from the language code automatically.
What if no quality value is specified? +
Languages without an explicit q-value default to q=1 (highest priority), following the HTTP specification.
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