moddl

Extend element

extend_element

Lengthens (or shortens) along the own axis: until a target set is reached, or by an amount; or turns one end to a point or a fall (to, slope: the other end stays, the length follows, a straight segment of one extrusion; Pset Gradient is named stale, never written). New revision, effect report (n_changed, rejected, cloned, carried). A call that succeeds is not a job that's done. Target: guid, guids or a set from find_elements/get_selection, never a filter. Beyond the named: PLAN_REQUIRED, run its plan_id with expect_beyond. The target is a set, never "anything near"; no hit is a refusal, not a number. Measured at the bodies. until.fit cut fits the end under sloped planar faces (a board under a roof slope), shortening where it reaches through; the volume is measured before writing.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "extend_element"
  }
}

Input Schema

Name	Required	Description
`by`	No	Or by this amount at each moving end (negative shortens)
`to`	No	Or this end lands on this point (one segment), turning about the other end
`end`	No	Which end moves, default the one facing the target; with to or slope required, start or end
`set`	No	A set id from find_elements or get_selection: writes exactly the elements seen there, nothing that matches later. An element changed since reading is rejected alone; the others are written
`guid`	No	One element (GlobalId)
`note`	No	Your note, stored with the new revision
`guids`	No	These elements (GlobalIds)
`slope`	No	Or this fall: '2 %', '1:50', '20 permille'; positive falls along the flow (its SINK to SOURCE port), else start to end; the moving end keeps its plan position
`until`	No	Extend until the body meets one of these
`dry_run`	No	Preview: the planned effect and a plan_id, nothing written
`plan_id`	No	Execute exactly the plan a dry_run returned, all or nothing; the plan holds target and fields. Plans that clone the same shared object (type, material) run one after the other: plan the second after the first ran, else PLAN_CHANGED
`request_id`	No	Your id for this call: a repeat answers the first result and writes nothing
`expect_count`	No	With set: how many elements the set holds - guards against a mixed-up set id
`expect_beyond`	No	With plan_id: how many elements the plan reaches beyond those named (n_beyond of PLAN_REQUIRED or the dry_run)
`expect_contacts`	No	Intended contacts: checks.contacts splits into as_expected, missing, surprises; an omitted kind is not judged

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 7, 2026

TDQS

A4.1/5.0

Behavior5/5

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

Beyond the annotations (readOnly=false, destructive=false, idempotent=false), the description discloses the write model: a new revision, a stale-element rejection that is per-element ('rejected alone; the others are written'), the plan_id all-or-nothing gate with PLAN_CHANGED for sequential clones, and request_id replay semantics. This is exactly the behavioral context annotations cannot convey, and nothing contradicts them.

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

Conciseness3/5

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

The scope and mode list are front-loaded, which is good, but the text is telegraphic and fragmentary ('A call that succeeds is not a job that's done.'), and parenthetical asides like the Pset Gradient remark add noise to an already dense block. It is readable but requires re-parsing, so it earns a middling score.

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

Completeness4/5

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

For a 15-parameter mutation tool with nested objects and no output schema, the description covers the workflow (dry_run to plan_id), the revision/effect report fields, contact expectations, and set-target safety. It is close to complete; only explicit escalation/alternative routing is thin.

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

Parameters4/5

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

Schema coverage is already 100%, so the 3 baseline applies, but the description adds real meaning: how until.fit=cut behaves under sloped planar faces ('a board under a roof slope'), that the volume is measured before writing, and that cut geometry is measured at the bodies. These clarify the trickiest nested parameter beyond its schema text.

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 first sentence states a specific verb and resource ('Lengthens (or shortens) along the own axis') and enumerates the three modes (to a target set, by an amount, to a point or fall). It implicitly separates the tool from move_elements or split_element by anchoring everything to the element's own axis. It stops short of explicitly naming a sibling to avoid, which keeps it from 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 Guidelines4/5

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

Usage conditions are clear: the target is guid/guids/a set from find_elements or get_selection and 'never a filter', beyond-bound operations require PLAN_REQUIRED and expect_beyond, and dry_run previews before plan_id executes. What is missing is explicit when-not guidance (e.g. when to use clip_elements or move_elements instead), so it lands at 4 rather than 5.

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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