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

Goes well beyond the annotations: overwrite-of-existing-key semantics, TTL of 1-30 days with a default of 30, values persisting until expiry or deletion, cross-region read lag up to a minute, billing model including free failed calls, and the blast radius ('changes only what you saved in your own memory namespace'). Annotations only supply the readOnly/idempotent/destructive flags, so this is substantial added context.

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?

The core action and its storage semantics are front-loaded and the paragraph is dense with useful facts. It loses a point for redundancy: TTL/expiry is stated twice ('expires after 1 to 30 days' and 'kept until they expire (at most 30 days)') and pricing is restated at the end.

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 4-parameter write tool with no output schema, the description covers lifetime, consistency, cost, scope of effect, and overwrite behavior, leaving nothing an agent needs in order to call it correctly.

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 the schema already documents the key length, value size, days range/default, and the namespace-as-password warning. The description restates the value size and TTL rather than adding new syntax or format guidance, so the 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 and resource ('Save a value ... under a key in your own namespace') plus the payload limit, and names memory_get as the read counterpart, which separates it from memory_get/memory_list/memory_delete in the sibling set.

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?

Explicitly says when to use it: 'Use to persist what an agent learned for a later call to memory_get,' and warns that each call is charged so repeats are not free. It does not mention the other siblings (memory_list for enumeration, memory_delete for removal), so the routing picture is clear but not exhaustive.

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