Block until a TwinCAT PLC symbol matches a comparison operator and value or a timeout expires; return whether it was met and elapsed time.
Block until symbol value (==, !=, >, >=, <, <=) or timeout. Returns met/elapsed.
| Name | Required | Description | Default |
|---|---|---|---|
| op | Yes | ||
| name | Yes | ||
| value | Yes | ||
| timeout_ms | No | ||
| interval_ms | No |
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
v0.6.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and destructiveHint=false, covering the safety profile. The description adds genuinely useful context beyond that: it will BLOCK until the condition is met or the timeout expires, and returns met/elapsed. However it omits operational details like polling behavior/interval and the risk of long blocking up to timeout_ms.
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?
Two tight sentences with the primary action front-loaded and zero filler. It is efficiently sized, though for a tool with five undocumented parameters the brevity edges toward under-specification rather than clean conciseness.
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?
The three required params (name, op, value) are all covered, an output schema exists so return-value detail is not required, and annotations cover safety. The two optional params (timeout_ms default 10000, interval_ms default 50) are left undocumented, leaving a real gap against 0% schema coverage.
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 carries the full param burden and must compensate. It does meaningfully document the `op` argument by enumerating the six comparison operators the schema leaves as a bare string, and it clarifies name/value roles. But timeout_ms and interval_ms (their defaults and units) are never addressed.
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 (block/wait) and resource (symbol compared against a value via an operator) with the timeout escape condition. An agent can grasp the core action, but the description never distinguishes it from near-siblings like ads_watch or ads_read, so differentiation is left to inference.
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 explains the mechanism but gives no when-to-use guidance, no prerequisites, and no named alternative (ads_watch is the obvious competing polling tool). The agent must infer the usage scenario purely from the blocking semantics.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.