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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds a cost signal ("Free") and the no-arg default, which is genuine added value, but "Free" is ambiguous and nothing is said about behavior on an invalid index or unknown hash.

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 short sentences, front-loaded with the primary operation and zero filler. The default behavior and cost note both earn their place.

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 two-parameter read tool with full schema coverage and no required arguments, the description is close to sufficient. The main omission is error/edge behavior (out-of-range index, hash with no passage), though no output schema exists to explain return shape.

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 both parameters (hash, index) are already fully documented in the schema, including the 0-based indexing and the meaning of the hash. The description only restates the two modes and adds no format or constraint detail 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?

States a specific verb and resource ("Read one passage") and enumerates the two lookup modes (index, transaction hash) plus the no-argument default. It is clear enough to act on, but it never distinguishes itself from the sibling read_last, which the no-argument behavior appears to duplicate.

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 one implicit usage rule — omit all arguments to get the last passage — but does not say when to prefer hash over index, nor when to call read_last instead of this tool. Usage is inferable from the sibling list but not stated.

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