Diff

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

Annotations already establish readOnlyHint=true and openWorldHint=false, so safety is covered. The description earns its place by defining what the result actually contains (both things that began and things that stopped being believed), which matters because there is no output schema. It says nothing about ordering, volume, or handling of the open-ended 'to' default beyond what the schema notes.

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, no filler: the definition comes first, the usage scenario second. Every clause carries meaning and nothing repeats the name or title.

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 two-parameter read-only tool with full schema coverage and no output schema, the description supplies the one thing structured data cannot: what a 'diff' means in this belief model and what the result enumerates. Only the ordering/shape of the returned set is 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 coverage is 100% and both parameters already document the RFC3339 format and the 'omit for now' behavior for `to`. The description reinforces the notion of two instants but adds no syntax or edge-case detail beyond the schema, so the baseline of 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?

The description states a specific operation with a precise semantic definition: the set of things that began or stopped being believed between two instants. This distinguishes it in substance from remember/recall/forget, though it never names the closest sibling (history) so the agent must infer the boundary.

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 concrete when-to-use framing — 'to say what changed over a period, such as since the last session or during an incident' — which maps real scenarios onto the tool. It stops short of stating exclusions, e.g. when to prefer history over diff.

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