place_widget

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

With no annotations, the description carries the behavioral burden and does so well: it discloses that live sources re-run server-side with no LLM, that 'NOTHING runs until the human clicks Approve on the canvas,' that approved sources go on a persistent allow-list, that livemap nodes light up on matching file edits, and that source output must match the widget data shape. These are non-obvious, high-consequence behaviors the schema does not express.

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?

Purpose and return value are front-loaded in one sentence, then a tight bulleted payload catalogue follows. It is long, but nearly every line is load-bearing for an 8-kind polymorphic tool; only the parentheticals (e.g. 'sortable', 'monospace log/output') shade into extra detail.

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 complex, nested, no-annotation tool this covers the essentials: kinds, payload shapes, live-source gating, refresh interval, and the returned id. It omits secondary behavior an agent might need — default layout/size handling for h/w/w, whether an existing id collides or updates, and any widget-count limits — but nothing that blocks a correct call.

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?

The schema's `data` field is a bare 'Payload matching the kind (see description)' pointer, so the description is the only place the per-kind payload contracts are defined (table columns/rows, chart type/labels/values/linkTo, metric, kv, status-list statuses, livemap nodes/globs/edges). At 75% coverage with 8 params and deep nesting, this compensates fully for the schema gap.

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?

States a specific verb and resource ('Show something to the human on their mcp-screen canvas') and the return value ('Returns the widget id'), which clearly frames this as the creation/display tool. The eight-item widget-kind list reinforces that this is the create path. It never explicitly names or contrasts with update_widget or read_widget, so sibling differentiation is left implicit.

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?

Usage is implied rather than stated: the widget-kind catalogue tells the agent what it can render, and the first sentence implies 'use this when you want the human to see something.' There is no explicit statement of when to prefer place_widget over update_widget, post_report, or ask_user, and no stated exclusions.

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