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

With no annotations, the description carries the full behavioral burden and mostly fails it: nothing about what a write overwrites or appends, whether the store is shared across sessions, auth requirements, or reversibility. "data-only by default" is a real hint that a different (presumably non-data/metadata) mode exists, but it is left unexplained.

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?

One short, front-loaded sentence with no waste. It is efficiently sized, though the ambiguous parenthetical raises more questions than it answers.

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 mutation tool with no annotations and no output schema, the definition is too thin: an agent cannot tell what is being stored, what "default" mode means, what the alternative mode is, or what the call returns. The zero-param schema is simple, but the behavioral gap remains.

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?

The tool takes zero parameters, so the schema-baseline of 4 applies; there are no parameter semantics the description could usefully add beyond confirming the tool is bodyless.

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 (Write) and resource (the shared store), and the sibling list makes the read/write split with store_read obvious. The parenthetical "data-only by default" hints at a non-data mode without naming it, so the scope is not fully pinned down.

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?

No when-to-use guidance and no explicit alternative routing, though the existence of store_read makes the read counterpart inferable. "data-only by default" implies another mode exists but never says when to use which.

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