utxo_sign

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full behavioral disclosure burden and does so by warning that private keys may be logged or stored in conversation history, and restricting use to trusted local environments. It also clarifies that the private key comes from a parameter, never an environment variable. A minor gap is the absence of return-format or broadcast-behavior details.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is only three sentences, front-loaded with the core purpose, then the two action modes, and finally a crucial security warning. Every sentence earns its place without repetition or filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a multi-chain, multi-mode signing tool with no annotations and no output schema, the description covers the essential aspects: supported assets, two invocation paths, required input metadata, and the private-key security caveat. It would be stronger if it stated the return value (e.g., signed transaction hex) and whether broadcasting occurs, but overall it is quite complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema exposes no properties, so the description is the only source of parameter meaning. It explains the key data required: a prepared transaction object for one action, or raw unsigned hex with script and satoshis-per-input metadata for the other, plus the private-key parameter. However, exact parameter names or the action-selection identifier are not specified, so full invocation cannot be constructed from the description alone.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific verb and resource: 'Sign a UTXO transaction' and explicitly lists the supported chains (bitcoin, bitcoin-cash, litecoin, dogecoin, dash, zcash), making the tool's purpose unmistakable. It also naturally distinguishes itself from sibling signing tools by scoping to UTXO-chain assets.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description clearly outlines two usage modes: 'sign-from-details' for prepared transaction objects and 'sign-unsigned-hex' for raw unsigned hex with inputs metadata, giving the agent actionable guidance on when to use each. It does not explicitly name alternative tools like evm_sign, but the chain scope and mode breakdown provide sufficient context.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.