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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered structurally. The description adds non-obvious behavior beyond that: the response includes an etag and how it is consumed downstream, which is valuable with no output schema. Missing error/absence semantics (what happens if the key does not exist) keeps it at 4.

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?

A single sentence with a parenthetical that carries the return-value and round-trip semantics; the core action is front-loaded and nothing is wasted. The parenthetical earns its space because it encodes the etag workflow.

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 correctly compensates by disclosing that the return is value + etag, and annotations cover the read-only nature. The main remaining gap is not stating key-not-found / empty-locker behavior, which an agent might need to handle.

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 every parameter (key, instance_id, passport_token) is already fully documented in the schema, and the description adds no syntax or format detail for them. The "pass it as if_match" note concerns an output field and a parameter of a different tool, not this tool's inputs. 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+resource ("Read a value from your memory locker") and immediately ties it to the locker_put counterpart, so the agent can distinguish read from write. It does not explicitly contrast with the other read-ish sibling locker_list, which keeps it short of 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?

Gives concrete follow-up guidance: the returned etag should be passed as if_match to locker_put to perform a conditional replacement. That is real when-to-use context rather than filler. It stops short of 5 because it never states when NOT to use this tool versus locker_list or locker_delete.

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