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ass_shift_times

Shift ASS subtitle line start and end times by a millisecond offset, including negative values to move lines earlier, with optional clamping to preserve relative timing.

Instructions

Shift the start/end of lines by offset_ms (negative shifts allowed).

Args: selection: which lines to shift — None/"all", an index, a list of indices, "0-4,7" or any selector base.resolve_indices takes. offset_ms: milliseconds to add; negative values move lines earlier. doc_id: document id; defaults to the current document. clamp: when True the shift is limited so that no selected line starts before zero. The same (reduced) offset is applied to every line so the relative timing of the selection is preserved. only_selected: when False every line in the document is shifted and selection is ignored.

Returns: {"doc_id", "requested_offset_ms", "applied_offset_ms", "clamped", "only_selected", "indices", "count", "applied", "changes": [{"index", "start_ms", "end_ms", "new_start_ms", "new_end_ms", "start", "end"}]} where the new_* values are what the document actually holds after the write (ASS stores centiseconds).

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
clampNo
doc_idNo
offset_msNo
selectionNo
only_selectedNo

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

A4.1/5.0
Behavior4/5

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

With no annotations, the description carries the full burden and does it well: it explains clamp limits each line to not start before zero and that the *same reduced* offset applies to preserve relative timing, and it notes ASS stores centiseconds. It stops short of stating permission needs or reversibility, but the mutation behavior is unusually well disclosed.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the core action, then cleanly sectioned into Args and Returns, with no padding in the argument prose. The detailed Returns block is somewhat redundant given an output schema already exists, which keeps it from a perfect score.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 5-parameter, 0%-schema-coverage mutation tool with no annotations, the description covers every parameter's behavior plus clamping edge cases and the write semantics. An output schema exists and is even summarized, so nothing an agent needs to invoke this correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must compensate and it does: selection (with accepted formats including None/"all", index, list, "0-4,7", resolve_indices selectors), offset_ms (negative moves earlier), doc_id default, clamp semantics, and only_selected=False ignoring selection. Every one of the 5 parameters is given meaning beyond the bare schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description gives a specific verb + resource ("Shift the start/end of lines by offset_ms") and notes negative shifts are allowed, so an agent immediately understands it is a relative timing mutation. It does not explicitly distinguish itself from siblings like ass_set_times, ass_scale_times, or ass_fix_timing, so it stops short of a 5.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is only implied through parameter semantics (only_selected, clamp, selection formats); there is no explicit statement of when to choose this over ass_set_times or ass_scale_times, nor any prerequisites. The agent can infer intended usage but is given no routing guidance or exclusions.

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

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