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

Annotations are all false (readOnly=false, destructive=false, etc.), so the description carries the full burden and does a good job: it discloses that the card is a real cut (not overlay), that spoken-word captions never appear on it, that it shifts subsequent content, and that it returns the project identity. Minor gaps remain—it doesn't discuss reversibility or effects on other tracks—but the disclosed behavior is substantial.

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 description is dense but efficiently organized: it front-loads the critical scope, then explains the behavior, then parameter hints, then the alternative. Every sentence adds value—no filler—though it could be tightened slightly by moving the explicit alternative to the end, which it already does. It's appropriately sized for the complexity.

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 13 parameters, 4 enums, and no output schema, the description is not complete. It doesn't explain the enum options (entrance, exit, template, font) or their effects, doesn't specify defaults for duration_s or size_scale, and doesn't detail the return value beyond 'project identity'. The description covers only the core behavior and a couple of params, leaving too much for an agent to guess or investigate.

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 only 8%, and the description compensates for only a few parameters: at_output_s (program seconds), bg_color (default '#000000'), subtitle (adds a second line), and text (implied as the main text). The remaining 10 parameters (exit, font, color, entrance, template, duration_s, size_scale, accent_color, project_id, etc.) are unexplained, leaving the agent to infer or open the schema for each. This is insufficient for a low-coverage 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 ('add_title_card' builds a standalone full-frame card with text) and immediately scopes it as project-limited. It also distinguishes itself from the sibling add_text by explaining the difference (card replaces footage vs. text overlays on it), so an agent can tell them apart without inspecting schemas.

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?

Explicitly states when to use it ('when the text should sit OVER the footage rather than replace it' is the exclusion for add_text) and clarifies the timing semantics (at_output_s is program seconds, everything shifts later by duration_s). It also notes the project_id is immutable and copied from specific sources, giving clear invocation guidance.

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