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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the description rightly spends its words elsewhere: it discloses the response shape, that each fact names its source and carries a permission label, and that facts cite block/transaction/log index with a reproducing RPC command. The most valuable addition is the caveat that a 'nothing indexed (blocks X..Y)' note covers only that range and does not mean nothing happened on chain, which prevents a false negative inference.

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 sentences, front-loaded with the outcome and followed by the caveat, with little wasted wording. The parentheticals are dense to the point of opacity ('permission label of shape (a) to (e)'), which costs a bit of clarity but not length.

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 must explain return values, and it does so only partially: the permission labels (a)–(e) are referenced but never defined, and nothing is said about result size, ordering, or limits despite promising 'every fact'. The empty-range caveat is a genuine completeness win, but the return contract remains under-specified.

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%, with both address and chainId documented including example chain ids, so the schema carries the parameter burden. The description only restates the chain scoping ('on one chain') and the path form, adding no format or validation detail beyond what the schema already provides.

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 ('Returns every fact the reader has indexed about an address on one chain') and pins the scope to a single chain plus a concrete endpoint shape (GET /read/:chainId/:address). An agent knows exactly what it gets back 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?

There are no siblings to route against, but the description never explicitly states when to call this tool or what its prerequisites are. Usage is only implied by the resource description, and the one interpretive rule given (the empty-range note) is about reading results rather than choosing the tool.

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