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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered by structured data. The description adds only the notion of named record types and no failure semantics (e.g., missing key or wrong store), which is the one piece of behavior an agent could genuinely use here.

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 with the core action front-loaded and no filler. The second sentence is only mildly informative but is cheap and points at intended record key values.

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 explain return values, and annotations cover the safety profile; parameter documentation is complete in the schema. The only real omission is error/not-found behavior for a lookup tool, which keeps it from a 5.

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% and both parameters are documented, including the 'username~store-name' form of the store id in the schema. The description's 'by store id and record key' merely restates the schema, 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?

The description states a specific verb and resource ('Returns one record from a key-value store') and names the two lookup dimensions (store id, record key), so an agent knows exactly what the tool fetches. It does not need to differentiate from siblings, which are entirely unrelated integrations, but it also does not call that out.

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 for INPUT, OUTPUT, or other named records' gives a hint about which record keys are meaningful, implying the tool is for retrieving named payloads. There is no explicit when-not guidance, no alternative retrieval tool named, and no statement about what happens for a missing key.

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