diff_since

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

Annotations already establish that this is a safe, non-destructive, closed-world read. The description goes further by disclosing the tolerance-based change-detection rule, that topology and material_slots are attached only when they differ, and the useful edge case that size-preserving edits still surface. It doesn't cover pagination or volume limits, which keeps it from a 5.

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 change-detection result is front-loaded, then the optional topology/material_slots detail, then usage. Dense but every sentence carries information; only the parenthetical before -> now phrasing is slightly repetitive.

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?

With no output schema, the description usefully specifies what the return contains, including the conditional topology and material_slots fields. The main gap is the unexplained `name` parameter, but for a read-only diff tool the definition is otherwise sufficient 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 0%, so the description carries the burden. It explains `tolerance` well (change threshold in metres, applied to movement and size), but `name` — the checkpoint reference with default 'last' — is never explained, leaving half the parameters to inference.

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 names a specific operation and resource — a diff of the scene since a checkpoint — and enumerates exactly what appears in the result (added, removed, moved/resized objects with before-and-now sizes). It is immediately distinguishable from siblings like checkpoint, rollback, and scene_tree.

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 usage contexts: 'review a long session' or 'see what a tool did'. That is clear when-to-use guidance, but it offers no exclusions or explicit routing against the closest siblings (checkpoint, rollback, scene_tree), so it stops short of a 5.

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