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

Annotations already declare readOnly/idempotent/non-destructive, and the description still layers on substantial behavior: zero balances are omitted, per-chain data sources (Blockscout for 4663, Moralis for 143), Solana lamport/rent semantics, and pre-failure conditions for ATA rent. This is exactly the extra context annotations cannot carry.

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?

Purpose and the connect_drop prerequisite are front-loaded, and each subsequent sentence carries chain-specific operational detail rather than filler. It is dense and long for a one-parameter tool, but the Solana rent/fee figures are decision-relevant rather than padding.

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 correctly explains the return semantics (omitted zero balances, per-chain token sourcing) as well as the preconditions for a successful downstream drop. An agent has enough to both interpret the result and decide whether a send can proceed.

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 coverage is 100% for the single chainId param, so baseline is 3, but the description adds real meaning beyond the schema: it documents special behavior for chainId 4663, 143, and 1399811149 that the schema's one-line description does not convey.

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 and resource ('Get native and token balances for the API key owner embedded wallet') and scopes it further by naming which chains are accepted. It also explicitly positions itself relative to the connect_drop sibling via 'Always call before connect_drop', so an agent can distinguish intent without opening the 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?

Gives a clear when-to-use directive ('Always call before connect_drop') and states the accepted chain classes. It does not name any when-not condition or an alternative tool for balances outside Smart Send/delegation chains, so it stops short of full routing guidance.

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