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

Annotations mark this as non-read-only, non-idempotent, and non-destructive. The description adds meaningful context beyond that: storage is scoped to the calling account/caller and read back only for that same caller, and diff is stateful relative to the last save or pull. It stops short of describing rate limits or the return shape.

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?

Four sentences, front-loaded with the save-then-diff purpose, followed by action semantics and the caller-scoping constraint. Efficient and well ordered, though the enumeration of params is somewhat redundant with the schema.

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 an 8-param, mutation-capable tool with no output schema, the description covers the stateful save/diff model, caller-scoped persistence, and what diff returns (signals not in the saved set). That is close to complete, with only return format and pagination left implicit.

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 itself notes which params apply on save vs diff (e.g., 'Ignored on diff'). The description restates the save-side params but adds no syntax or format detail beyond the schema, so the baseline of 3 is appropriate.

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 states a specific verb pair (save/diff) on a specific resource (a named space in the Whimbrel signal index), and the title reinforces it. An agent can understand what the tool does. It does not, however, distinguish itself from the sibling space_scan, which sounds related.

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 clearly explains the two action modes ('action save stores...', 'action diff returns...'), which implies when each is used. But it gives no guidance on when to prefer this over siblings like find_signals, latest_signals, or space_scan, and states no exclusions or prerequisites.

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