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

Beyond the annotations (readOnly/idempotent/non-destructive), it discloses two non-obvious behaviors: the response preserves the original Content-Encoding, and the call requires an x402 payment signature in _meta["x402/payment"]. Payment/auth requirements and response-encoding caveats are exactly the context annotations cannot convey.

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?

Front-loaded with the core purpose and scoping constraint, then payment requirements last. The USAGE line partially restates the opening paragraph and the examples are somewhat boilerplate, but nothing is bloated or buried.

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 a rich annotation set, full schema coverage, and an output schema (so return values need no explanation), the description supplies everything remaining an agent needs: exact-key requirement, encoding behavior, and the x402 payment prerequisite.

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% and both parameters (recordKey, keyValueStoreId) are already documented in the schema. The description only adds the 'requires the exact key name' constraint, which is marginal extra meaning — the baseline 3 applies when the schema does the heavy lifting.

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 first sentence states a specific verb (get), resource (value/record in a key-value store), and explicitly scopes it as a single record rather than a key listing. An agent can classify the tool 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?

"Use when you need to retrieve a specific record (JSON, text, or binary) from a store" gives clear triggering context, and the 'not a listing of all keys' clause rules out a competing interpretation. It stops short of naming a concrete alternative tool or explicit when-not conditions, so it is not a 5.

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