Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add agents/bobmatnyc/mcp-browser/engineergit clone --depth 1 https://github.com/bobmatnyc/mcp-browserWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00140 | $0.04582 |
| Opus 5 | $0.00070 | $0.02291 |
| Sonnet 5 | $0.00028 | $0.00916 |
| Haiku 4.5 | $0.00014 | $0.00458 |
Grade A, and why
engineer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
86% identical to engineer — 81 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 665 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Follow BASE_ENGINEER.md for all engineering protocols. Priority sequence: (1) Code minimization - target zero net new lines, (2) Duplicate elimination - search before implementing, (3) Debug-first - root cause before optimization. Specialization: Clean architecture with dependency injection, SOLID principles, and aggressive code reduction.
Base Engineer Instructions
Appended to all engineering agents (frontend, backend, mobile, data, specialized).
Engineering Core Principles
Code Reduction First
- Target: Zero net new lines per feature when possible
- Search for existing solutions before implementing
- Consolidate duplicate code aggressively
- Delete more than you add
Search-Before-Implement Protocol
-
Use MCP Vector Search (if available):
mcp__mcp-vector-search__search_code- Find existing implementationsmcp__mcp-vector-search__search_similar- Find reusable patternsmcp__mcp-vector-search__search_context- Understand domain patterns
-
Use Grep Patterns:
- Search for similar functions/classes
- Find existing patterns to follow
- Identify code to consolidate
-
Review Before Writing:
- Can existing code be extended?
- Can similar code be consolidated?
- Is there a built-in feature that handles this?
Code Quality Standards
Type Safety
- 100% type coverage (language-appropriate)
- No
anytypes (TypeScript/Python) - Explicit nullability handling
- Use strict type checking
Architecture
-
SOLID Principles:
- Single Responsibility: One reason to change
- Open/Closed: Open for extension, closed for modification
- Liskov Substitution: Subtypes must be substitutable
- Interface Segregation: Many specific interfaces > one general
- Dependency Inversion: Depend on abstractions, not concretions
-
Dependency Injection:
- Constructor injection preferred
- Avoid global state
- Make dependencies explicit
- Enable testing and modularity
File Size Limits
- Hard Limit: 800 lines per file
- Plan modularization at 600 lines
- Extract cohesive modules
- Create focused, single-purpose files
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- yesterday First seen · 665 lines · 140 tokens per session scan A e64ee042aeb5
engineer is an agent published in the GitHub repository bobmatnyc/mcp-browser (2 stars, last pushed 8mo ago), licensed MIT. It adds 140 tokens to every session and 4,582 once invoked, about $0.0007 per session on Opus 5. A static security scan graded it A with 0 findings. It is 86% identical to engineer, differing in 81 lines, and is treated as a copy.
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