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

Annotations already declare readOnly, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds value by stating the return is plain text and giving the underlying REST route, though it says nothing about behavior for out-of-range or very large indexes.

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?

Two short sentences, fully front-loaded with the operation and result, then the REST mapping. No filler.

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 an output schema present, the description need not detail return values, and it still notes plain-text output. Slightly incomplete only in not covering failure behavior for an invalid index in a lookup tool that an agent may call with user-supplied input.

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%, with the parameter documented as 'Global transaction index across the chain' including the genesis example. The description restates that same idea ('global transaction index') without adding format, bounds, or lookup-cost detail, so 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 and resource: retrieve the transaction ID (txid) at a given global transaction index, plus the REST route. It does not name or contrast with siblings such as get_block_txid or get_block_txs_from_index, which is the only thing keeping it from a 5.

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 phrase 'global transaction index' implies the use case, and the schema note ('For an in-block position, use `BlockTxIndex` instead') clarifies the alternative. That distinction lives in the schema, however, not the description, so guidance here is only implied.

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