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

Annotations already declare readOnlyHint=true, and the description adds value by detailing the parsed header fields returned (hash, version, previous block hash, merkle root, timestamp, bits, nonce). It does not mention error cases or rate limits, but the read-only nature and return shape are well covered.

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 a single, well-structured sentence that front-loads the purpose and lists the output fields efficiently. Every word serves a purpose, with no redundancy or fluff.

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?

This is a simple one-parameter read tool with no output schema, and the description fully covers what is returned. It lists all key fields and specifies the network, making it adequate for an agent to select and invoke correctly without additional context.

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 only parameter 'height' is fully described in the schema, and the description reinforces that height is the input for fetching block header data. Since schema coverage is 100%, the description adds minimal extra semantic value beyond 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 clearly states the tool gets block header data by height on Bitcoin testnet3, listing specific return fields. It distinguishes itself from siblings like btc_get_block (mainnet) by explicitly naming the testnet network.

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 implies usage for Bitcoin testnet3 by height but does not explicitly state when to use this tool over alternatives like btc_get_block for mainnet. No exclusions or alternative tool names are mentioned, so guidance is implicit.

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