Add arbitrary transaction skill

[stuckinaboot]

Adds support for submitting raw EVM transactions with explicit calldata:

• New reference doc: references/arbitrary-transaction.md
• Updated SKILL.md with capability section and prompt examples
• Added trigger phrases to description

[0xdeployer]

@claude

[claude]

Claude finished @0xdeployer's task in 1m 23s —— View job

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Code Review

Tasks

• Read repository guidelines (CLAUDE.md if present)
• Review bankr/SKILL.md changes
• Review bankr/references/arbitrary-transaction.md
• Provide comprehensive feedback

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Summary

This PR adds support for submitting raw EVM transactions with explicit calldata, a powerful feature for advanced users. The documentation is well-structured and comprehensive. I've identified several areas for improvement around clarity, security warnings, and completeness.

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bankr/SKILL.md

Strengths

✅ Description updated with clear trigger phrases ("submit raw transactions, execute calldata, or send transaction JSON")
✅ New capability section properly formatted and consistent with existing sections
✅ Prompt examples added in the appropriate location
✅ Reference link follows existing pattern

Issues & Suggestions

1. Missing Solana support clarification (bankr/SKILL.md:168-173)
The skill description mentions Solana support, but arbitrary transactions only work with EVM chains (Ethereum, Polygon, Base, Unichain). Consider adding a note in the capability section:

### Arbitrary Transactions
- Submit raw EVM transactions with explicit calldata (EVM chains only)
- Custom contract calls to any address
- Execute pre-built calldata from other tools
- Value transfers with data

2. Prompt examples could be more realistic (bankr/SKILL.md:345-348)
The current examples use placeholder syntax that might confuse users:

• {to: 0x..., data: 0x..., value: 0, chainId: 8453} - This isn't valid JSON (no quotes)

Consider showing a more concrete example or at least using proper JSON syntax:

- "Submit this transaction: {\"to\": \"0x1234...\", \"data\": \"0xa9059cbb...\", \"value\": \"0\", \"chainId\": 8453}"

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bankr/references/arbitrary-transaction.md

Strengths

✅ Excellent table-based format for validation rules and troubleshooting
✅ Clear JSON schema with all required fields documented
✅ Good security notes section
✅ Practical use cases and best practices
✅ Multiple prompt examples covering different scenarios

Issues & Suggestions

1. Incomplete example addresses (bankr/references/arbitrary-transaction.md:47-48)
Line 48 shows: "data": "0xa9059cbb000000000000000000000000recipient00000000000000000000000000000000000000000000000000000000000f4240"

The word "recipient" in the middle of hex data is confusing. This should either be:

• A complete, valid example with proper address encoding
• A placeholder with clearer notation like [ADDRESS_HEX]

Similar issues on lines 57, 69, 80, 81 with "0xContractAddress...", "0xRecipientAddress...", "0xTokenContractAddress..."

Fix examples →

2. Security warnings could be more prominent (bankr/references/arbitrary-transaction.md:112-118)
Given the high-risk nature of arbitrary transactions, the security notes appear late in the document. Consider:

• Moving security notes earlier (perhaps right after JSON format)
• Adding a warning box or stronger formatting
• Including a note about the risk of malicious calldata

3. Missing information about gas estimation
The document mentions "Check gas estimates" in best practices (line 109) and "Insufficient funds" in common issues (line 95), but doesn't explain:

• Whether users need to calculate gas separately
• If the system estimates gas automatically
• How to know if you have enough balance

4. No mention of transaction simulation/preview
Does the Bankr API provide any simulation or preview before submitting? If yes, document it. If no, this is a critical missing feature that should be mentioned in security notes.

5. Value field type inconsistency (bankr/references/arbitrary-transaction.md:29)
The table says value is type "string", but in the JSON format example (line 21) it shows "value": "0" which is correct. However, the validation rules (line 38) could be clearer about:

• Why it's a string (to handle large numbers)
• Whether scientific notation is supported
• Maximum value constraints

6. Typo in table header (bankr/references/arbitrary-transaction.md:7)
Minor: The table has "Chain | Chain ID" but would be more consistent with other tables to use "Name | Chain ID" or similar.

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Testing & Validation Questions

1. Are there any scripts (bankr-submit.sh, etc.) that need updates to handle transaction JSON format?
2. Does the API validate the transaction JSON before submission, or could malformed JSON reach the blockchain layer?
3. Rate limiting: Are arbitrary transactions subject to the same rate limits as other operations?
4. Confirmation flow: Do these transactions bypass or include user confirmation prompts?

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Overall Assessment

Quality: Good - The documentation is comprehensive and well-organized
Completeness: 85% - Missing some critical security context and edge case handling
Risk Level: High - This feature grants direct blockchain access, security documentation is critical

Recommendation

This PR is on the right track but would benefit from:

1. Stronger, earlier security warnings
2. More complete/realistic examples
3. Clarification about gas handling and transaction simulation
4. Addressing the Solana vs EVM-only distinction

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| Branch: aspyn/add-txn