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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavioral information: it returns an etag and that etag enables optimistic-concurrency replacement via locker_put. It omits what happens when the key is absent, but that is a minor gap given annotation coverage.

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 front-loaded sentence with no filler; the etag guidance is packed into a parenthetical instead of a separate paragraph. Every clause carries information.

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 convey return values, and it does say an etag accompanies the value. It stops short of describing the value's format (text/binary) or the missing-key behavior, which would fully close the loop for a read tool.

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 all three parameters (key, instance_id, passport_token) are already documented in the schema, and the description adds no parameter-level detail. Baseline 3 is appropriate 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?

States a specific verb ('Read') and resource ('a value from your memory locker') and names the returned etag, so the operation is unmistakable. It does not, however, distinguish itself from sibling locker_list or say when a caller should read one key vs enumerate keys.

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?

The parenthetical explains what to do with the returned etag (pass it as if_match to locker_put), which is usage guidance for the output rather than for selecting this tool. There is no explicit 'use this when / not when' or comparison against locker_list.

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