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

Adds meaningful context beyond the annotations: it returns UNSIGNED tx bytes simulated against mainnet, never signs or submits, and never moves funds or holds keys, which reconciles the readOnlyHint=true on a transaction-building tool. It stops short of covering auth requirements or rate limits, but the safety/return profile is well disclosed.

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?

Front-loaded correctly with the action, but the 'UNSIGNED' return point is repeated twice and the closing 'Non-custodial...' plus 'Education only, not financial advice' boilerplate is generic across the toolset, diluting the concise core.

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?

With no output schema, the description usefully carries the return contract (unsigned tx bytes, simulated against mainnet) plus custody and scope limits. For a build-tx tool this is nearly complete, missing only submission/usage flow detail.

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 100%, so the schema already documents all four parameters (coin symbols, amount in human units, sender address, BalanceManager id). The description adds no parameter-level detail, so the baseline 3 applies.

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?

States a specific verb+resource+scope: 'Withdraw a coin from your own BalanceManager back to your address (always to the owner).' The direction (withdraw) and destination (owner) cleanly separate it from build_bm_deposit_tx without needing to open either schema.

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 purpose implies when to use it (to pull funds out of a BalanceManager), but there is no explicit when-to-use guidance, no prerequisites, and no reference to the sibling build_bm_deposit_tx as the reverse alternative. Usage is only inferable.

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