ass_split_line

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

With no annotations, the description carries the full behavioral burden and does substantial work: it states the error condition, that each half keeps at least one visible character, that override blocks preceding the cut are repeated, and which attributes survive on the second line. It omits undo/snapshot semantics beyond the terse 'Snapshot-backed' tag.

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 content is dense but front-loaded, opening with the core action before constraints and the return shape. It is slightly long for its subject, and the markdown emphasis and separate return-shape sentence repeat information the output schema already carries.

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 mutation tool with no annotations, the definition covers error behavior, cut semantics, preservation rules and side effects well enough to call correctly. Only the trailing snapshot note and the undocumented optional doc_id keep it from being fully self-contained.

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 must compensate, and it does for two of three parameters: 'index is 0-based' and 'at_ms accepts milliseconds or a time string' with a stated validity range. The optional doc_id parameter is left unexplained, which is the only gap against 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 states a specific verb and resource ('Split one line in two'), and adds the governing constraint ('strictly inside its span'), which lets an agent distinguish it from ass_merge_lines, ass_duplicate_lines and ass_karaoke_split. It never names a sibling explicitly, so it sits just below the sibling-differentiating tier.

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 a clear context of use plus the precise guard condition 'start < at_ms < end, otherwise ToolError', which tells the agent when the call is valid. It does not, however, contrast this with alternatives such as ass_merge_lines or ass_karaoke_split, so no exclusions are offered.

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