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

With no annotations, the description carries the disclosure burden; it adds meaningful behavioral context by requiring a free API key, noting per-key privacy, and explaining that deletions are relevant to quota management. It doesn't disclose whether deletion is irreversible or how missing keys are handled, but the auth and scoping details go beyond the bare schema.

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 with no filler; the action is front-loaded, and the use case plus auth requirement each earn their place. The developer link is included without bloating the description.

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 single-parameter delete operation with no output schema, the description is largely sufficient: it covers action, use case, quota context, auth, and privacy. It could add a note on return/error behavior, but the low complexity means this is only a minor gap.

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 schema already fully documents the single `key` parameter at 100% coverage, so the description adds no additional semantic information about it. Baseline 3 applies because 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?

The description opens with a specific verb and object ('Delete a stored key'), which clearly identifies the action and resource. This distinguishes memory_delete from siblings memory_get, memory_set, and memory_list, which all target the same store but with different operations.

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?

It gives an explicit use case ('clean up entries you no longer need') and a rationale (quota per API key), so an agent understands when to call it. It doesn't name alternatives or state when not to use it, so it lacks the full when/when-not contrast of a 5.

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