Context Compression

Context Compression

Purpose

Maximize information value per token in MCP responses through abbreviation, schema optimization, selective field inclusion, and efficient formatting.

When to Use

Apply when:

• Token budgets are constrained
• Responses are repetitive or verbose
• Large datasets need representation
• Multiple tools share similar data structures
• Response size directly impacts performance

Compression Techniques

1. Abbreviate Field Names

Before compression:

{
  "searchResults": [
    {
      "identifier": "a1b2",
      "symbolName": "authenticate",
      "fileLocation": "/src/models/user.ts",
      "lineNumber": 42,
      "confidenceScore": 0.95
    }
  ]
}

After compression:

{
  "results": [
    {
      "id": "a1b2",
      "name": "authenticate",
      "file": "/src/models/user.ts",
      "line": 42,
      "conf": 0.95
    }
  ]
}

Savings: ~30% fewer tokens

2. Flatten Nested Structures

Before:

{
  "response": {
    "data": {
      "results": {
        "items": [...]
      }
    }
  }
}

After:

{
  "results": [...]
}

Savings: ~40% fewer tokens

3. Use Arrays for Uniform Data

Verbose (objects):

[
  {"id": "a1", "name": "foo", "type": "fn"},
  {"id": "b2", "name": "bar", "type": "fn"},
  {"id": "c3", "name": "baz", "type": "fn"}
]

Compact (table):

{
  "cols": ["id", "name", "type"],
  "rows": [
    ["a1", "foo", "fn"],
    ["b2", "bar", "fn"],
    ["c3", "baz", "fn"]
  ]
}

Savings: ~35% fewer tokens for 10+ rows

4. Selective Field Inclusion

Full response:

{
  "id": "a1",
  "name": "authenticate",
  "type": "function",
  "file": "user.ts",
  "line": 42,
  "column": 5,
  "endLine": 48,
  "endColumn": 3,
  "signature": "...",
  "docs": "...",
  "created": "2024-01-15",
  "modified": "2024-02-10",
  "author": "...",
  "complexity": 7
}

Minimal response:

{
  "id": "a1",
  "name": "authenticate",
  "type": "function",
  "file": "user.ts",
  "line": 42
}

Savings: ~70% fewer tokens (use get_details(id) for full version)

5. Reference-Based Compression

Without references:

{
  "results": [
    {
      "name": "User.authenticate",
      "file": "/very/long/path/to/src/models/user.ts",
      "package": "com.example.userservice"
    },
    {
      "name": "User.validate",
      "file": "/very/long/path/to/src/models/user.ts",
      "package": "com.example.userservice"
    }
  ]
}

With references:

{
  "refs": {
    "f1": "/very/long/path/to/src/models/user.ts",
    "p1": "com.example.userservice"
  },
  "results": [
    {"name": "User.authenticate", "file": "f1", "pkg": "p1"},
    {"name": "User.validate", "file": "f1", "pkg": "p1"}
  ]
}

Savings: ~50% for repeated values

Compression Patterns by Use Case

Search Results

{
  "r": [  // results
    {"i": "a1", "n": "authenticate", "c": 0.95},  // id, name, confidence
    {"i": "b2", "n": "validate", "c": 0.70}
  ],
  "m": true,  // has_more
  "t": 127    // total
}

Status Checks

{
  "p": "running",  // status
  "u": "2h15m",     // uptime
  "m": "245MB",     // memory
  "c": 15           // cpu_percent
}

Lists with Metadata

{
  "items": ["a", "b", "c", "d", "e"],
  "t": 127,   // total
  "s": 5,     // showing
  "m": true   // more available
}

Token Budget Allocation

Allocate token budget by information value:

Information	Priority	Budget %	Example
Core data	High	60%	Search results, IDs
Metadata	Medium	25%	Counts, flags
Help text	Low	15%	Next steps, tips

Example allocation (200 token budget):

• Results: 120 tokens (60%)
• Metadata: 50 tokens (25%)
• Guidance: 30 tokens (15%)

Abbreviation Dictionary

Standard abbreviations for consistency:

id       → i
name     → n
type     → t
file     → f
line     → l
confidence → c
results  → r
total    → t
has_more → m
description → desc
reference → ref
function → fn
class    → cls
interface → ifc

Use in schemas:

{
  "i": "id",
  "n": "name",
  "t": "type",
  "c": "confidence"
}

When NOT to Compress

Avoid over-compression for:

• Small responses (<100 tokens) - overhead not worth it
• Critical error messages - clarity over brevity
• Security-related fields - explicit is safer
• User-facing documentation - readability matters

Example - Don't compress:

{
  "error": "Authentication failed",  // Keep clear
  "code": "AUTH_INVALID_CREDENTIALS",
  "message": "The provided credentials are invalid"
}

Compression + Readability Balance

Extreme compression (hard to read):

{"r":[{"i":"a1","n":"auth","t":"fn","c":0.95}],"m":1,"t":127}

Balanced compression:

{
  "results": [
    {"id": "a1", "name": "auth", "type": "fn", "conf": 0.95}
  ],
  "has_more": true,
  "total": 127
}

Recommendation: Compress field names moderately, keep structure clear.

Quick Reference

Compression checklist:

• Abbreviate verbose field names
• Flatten unnecessary nesting
• Use reference system for repeated values
• Select only needed fields by default
• Provide full version via get_details(id)
• Balance compression with readability
• Don't compress critical errors/security
• Document abbreviations in schema

Token savings hierarchy:

1. ID references - 70-90% savings (biggest win)
2. Selective fields - 50-70% savings
3. Flattening - 30-50% savings
4. Abbreviation - 20-35% savings
5. Table format - 25-40% savings for lists

Focus on ID references and selective fields first for maximum impact.