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

With no annotations provided, the description carries the full burden and delivers real behavioral context: it reveals that loop mode is applied in the same call, that elementId/property are factored out of the loop body, and that this is a multi-keyframe batched mutation. It does not state whether the call replaces or appends to existing keyframes on the track, which is a minor gap given zero annotation coverage.

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?

Three sentences with zero waste: purpose first, idiomatic context second, exclusion of the sibling alternative third. Every sentence earns its place and the critical scoping constraint is front-loaded.

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 5-parameter tool with no output schema and no annotations, the description is nearly complete: it covers purpose, scope constraints, the fold-in loop behavior, and sibling disambiguation against a very large tool set. The only missing pieces are what the call returns and whether existing track keyframes are replaced or appended — minor given the strength of the disambiguation and operation semantics.

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 80% (only 'property' lacks its own description, though its enum clarifies it), so the schema already documents most parameters. The description adds conceptual framing — that elementId/property scope the call and loop is folded into it — but provides no new format or value semantics beyond the schema.

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 precise verb+resource statement: 'Add many keyframes to ONE element's ONE property in a single call' — the singular scoping (one element, one property) is exactly what distinguishes it from siblings like set_keyframes_batch. It further frames the idiomatic use case (ripple dot pulse, snowflake fall, equaliser-bar wave), leaving no ambiguity about what this tool does.

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?

The description gives explicit when-to-use guidance ('The idiomatic form when every layer in a multi-element animation gets its own track') and names the concrete alternative with the condition that selects it: 'Use set_keyframes_batch instead when you need to mix elements/properties in one atomic call.' It also signals that set_track_loop is folded in, preventing a redundant call.

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