derive_xpub

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

Beyond the readOnlyHint annotation, the description adds that the operation works offline and requires a specific environment flag. It also communicates a safe workflow pattern (derive once, reuse the xpub), which is useful behavioral context not present in annotations.

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 compact and well-structured: a one-line purpose, a short requirement note, a workflow sentence, and a bulleted parameter list. Every sentence earns its place and the most important constraints are front-loaded.

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?

Given the output schema exists and annotations cover safety, the description is complete: it states prerequisites, purpose, usage pattern, and all parameter semantics. Nothing critical is missing for an agent to decide when and how to invoke this tool.

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?

Schema description coverage is 0%, so the description fully compensates by explaining every parameter: mnemonic, standard with allowed BIP values, passphrase optionality, account index, and network override. This gives the agent enough semantic detail to construct correct calls without opening the schema.

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 uses a specific verb ('Extract') with a clear resource ('account xpub/ypub/zpub from a seed phrase') and immediately distinguishes the tool by noting it works offline. It clearly separates this from sibling derivation tools like derive_addresses or derive_from_path by focusing on the seed-phrase-to-xpub output.

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 gives clear usage context: run once offline, capture the xpub, then keep later queries watch-only. It also states the required MCP_BITCOIN_ALLOW_MNEMONIC=true prerequisite, though it does not explicitly name alternatives or when not to use this tool.

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