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

With no meaningful annotation coverage (all hints false, no details), the description carries the behavioral burden and largely delivers. It discloses that the effect is 'Synthesized locally like the colour cards: NO image or video generation, always available, costs no generation credits', explains timing side effects ('everything after shifts later by duration_s'), and notes a non-obvious interaction ('No captions ever land on it (inserted media)'). No contradiction with the false annotations, which are consistent with a mutating effect.

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 every clause earns its place — scope, effect, cost profile, style enum, timing semantics, intensity, sound, and caption interaction are all covered with no repetition. It front-loads the core purpose and scope before parameter details. Slightly long, but the density is justified given the 6-parameter, low-coverage 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 a 6-parameter mutation tool with no output schema and 17% schema coverage, the description is nearly complete: it covers project scoping, style semantics, timing, duration, intensity, sound, and returns ('returns the project identity with its result'). The only minor gaps are default for duration_s and exact return shape beyond identity, which are acceptable given the absence of an output schema.

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 17% (just project_id is described), so the description must compensate and does thoroughly: it defines all three style enum values ('digital' vivid datamosh macroblocks + horizontal tearing, 'vhs' tracking band + scanlines + chroma bleed, 'static' TV snow/no-signal), clarifies at_output_s is 'PROGRAM seconds', specifies intensity 0-1 with default 0.7, and sound default true. This adds real meaning beyond the bare 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 uses a specific verb+resource (add + corrupt screen) and immediately explains the effect: 'Cut to a full-frame CORRUPT / glitch screen for a beat, then return to the footage — a datamosh-style transition BETWEEN sections.' This clearly distinguishes it from siblings like add_color_screen, add_freeze_frame, and add_screen_takeover by specifying its role as a transition between sections rather than a static insert.

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 clear usage context: it's a datamosh-style transition BETWEEN sections (e.g. 'podcast -> CORRUPT -> the next scene'), and offers timing guidance ('Keep it SHORT (0.3-1s reads as a hit; longer feels genuinely broken)'). It doesn't explicitly name sibling alternatives or state when NOT to use it, but the between-sections positioning provides strong contextual routing.

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