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

The annotations already declare readOnlyHint=true, openWorldHint=true and idempotentHint=false, and the description adds real context beyond that: the exact upstream data sources (blockchain.info, a public Ethereum RPC node, Solana mainnet RPC), that no API key or signup is needed, and the security caveat that a generated private key is transmitted once and not stored. What it does not disclose is the shape of the result (units, precision, native vs. token balances) or failure behavior for a malformed address, which matters given there is no output schema. Note that a key-pair-generating operation sitting under readOnlyHint=true is unusual, though generating and returning a key pair does not modify server state, so this is not a contradiction.

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?

Three sentences, all of which carry information, and the no-API-key line is front-loaded value. However, the opening sentence is a long run-on fragment that stacks three chains, three providers and a second operation into one clause, which hurts scannability for an agent parsing it quickly.

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 3-parameter tool with no output schema, the description should at least hint at what a balance result contains (currency units, decimals, whether it reflects confirmations) and what happens on an unknown or malformed address. It covers inputs, providers and the key-handling caveat well, but leaves the return value entirely undefined.

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% and both enums are documented in the schema itself, including that address is 'balance only' and that new_wallet generates a key pair sent once and not stored. The description largely restates those facts (public address, generated key pair) without adding format or validity requirements. Baseline 3 is appropriate when the schema carries the semantics.

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 names the concrete resource (balance of a public Bitcoin, Ethereum or Solana address) and the alternate mode (a newly generated key pair), so an agent can tell it apart from every sibling, none of which touch crypto keys or chain balances. It is a noun phrase rather than a verb-first statement and never uses the schema's operation names (balance / new_wallet), so the mapping from intent to call is slightly inferential.

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?

There is one real usage rule: a generated private key transits the service, so it should be used only for tests and small amounts. That is a genuine when-to-use constraint, but there is no guidance on when to pick balance vs new_wallet, nor any exclusion such as chains that are unsupported or addresses that will fail validation.

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