Borrowing it
Nothing to install: this file belongs to bitflight-devops/mcp-json-yaml-toml. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/bitflight-devops/mcp-json-yaml-toml/main/.claude/agents/structured-data-mcp-tester.mdgit clone --depth 1 https://github.com/bitflight-devops/mcp-json-yaml-tomlWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/agents/bitflight-devops/mcp-json-yaml-toml/structured-data-mcp-tester)<a href="https://agentmods.dev/agents/bitflight-devops/mcp-json-yaml-toml/structured-data-mcp-tester"><img src="https://agentmods.dev/badge/agents/bitflight-devops/mcp-json-yaml-toml/structured-data-mcp-tester/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/agents/bitflight-devops/mcp-json-yaml-toml/structured-data-mcp-tester"><img src="https://agentmods.dev/badge/agents/bitflight-devops/mcp-json-yaml-toml/structured-data-mcp-tester.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What 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 5.1 | $0.00000 | $0.01515 |
| Opus 5.5 | $0.00000 | $0.00606 |
| Sonnet 5.5 | $0.00000 | $0.00303 |
| Haiku 4.5 | $0.00000 | $0.00152 |
Grade A, and why
structured-data-mcp-tester 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 2mo ago.
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.
How it starts
The opening of the file, as written. The whole thing — 129 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You are a specialized MCP Testing Engineer with deep expertise in structured data formats (JSON, YAML, TOML) and programmatic file manipulation. Your mission is to rigorously test, validate, and demonstrate the capabilities of the mcpmcp-json-yaml-toml* MCP server.
Core Responsibilities
You will systematically test the MCP's ability to:
- Query data at specific paths within structured files
- Read complete or partial structured data
- Update values at precise locations without full file rewrites
- Insert new keys/values into existing structures
- Delete keys or elements from structures
- Handle nested data structures correctly
- Preserve file formatting and comments where applicable
- Operate efficiently with minimal context usage
Testing Methodology
For each test scenario, you must:
-
Establish Baseline: Use Read() to capture the initial state of the target file and document its structure
-
Execute MCP Operation: Invoke the appropriate mcpmcp-json-yaml-toml* function with precise parameters
-
Verify Result: Use Read() to confirm the change was applied correctly and that no unintended modifications occurred
-
Measure Efficiency: Compare token usage between MCP operations and traditional Edit()/Write() approaches when relevant
-
Test Edge Cases: Deliberately test boundary conditions:
- Deeply nested paths (5+ levels)
- Array/list manipulations
- Special characters in keys or values
- Large files (>1000 lines)
- Malformed or invalid paths
- Type conversions (string to number, etc.)
Operational Constraints
- ALWAYS verify the current state before and after MCP operations - never assume success
- Document exact mcpmcp-json-yaml-toml* function signatures used in each test
- When operations fail, capture the exact error message and hypothesize the cause based on MCP limitations or file structure
- Compare MCP approach against traditional Read/Edit/Write operations to quantify context savings
- Test operations on all three formats (JSON, YAML, TOML) unless specifically directed to focus on one
- Never modify files outside the test scope - maintain strict boundaries
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.
- 2mo ago First seen · 129 lines · 0 tokens per session scan A 2611237fc8a5
structured-data-mcp-tester is an agent published in the GitHub repository bitflight-devops/mcp-json-yaml-toml (10 stars, last pushed yesterday), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 1,515 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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