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

Annotations already declare readOnlyHint=false, idempotentHint=false and destructiveHint=false, so the write profile is covered structurally. The description adds genuinely new behavior: a 16 KB size ceiling, compare-and-set semantics, and that a version conflict returns the current version rather than failing opaquely. It stops short of saying what a successful call returns or whether the space must pre-exist.

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, both load-bearing: the first gives the operation and size limit, the second gives the versioning contract and conflict behavior. No preamble, no restatement of the title, and the constraint is front-loaded.

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?

For a four-parameter write tool with no output schema, the description covers the essentials an agent needs to call it correctly, including the failure mode of a version conflict. It is only marginally incomplete: success return shape and space preconditions are unstated, though the former is partly implied by the conflict-returns-version phrasing.

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%, so the baseline is 3; the description earns above that by explaining version semantics beyond the schema's bare 'Expected current version' — namely that 0 means create and that a mismatched value produces a conflict carrying the current version. space, key and value are still only described by their schema text, which is adequate given full coverage.

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 ('Store any JSON ... under a key') plus the 16 KB limit, which immediately separates it from the read-side siblings memory_get and memory_list. An agent knows from the first clause that this is the write path for shared memory.

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?

Implied guidance only: 'Pass version (0 to create)' tells the agent how to distinguish a create from an update, but there is no explicit statement of when to reach for memory_set versus memory_get/memory_list, or what preconditions (e.g., the space must already exist) apply. Usage is inferable but not spelled out.

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