Block until a proxy breakpoint pauses a request or response flow, then return that paused flow for resumption.
Block until one of your breakpoints pauses a flow, then return it for resume_breakpoint.
| Name | Required | Description | Default |
|---|---|---|---|
| url | No | URL substring or * pattern | |
| phase | No | ||
| timeout_seconds | Yes | 1..300 |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description's real contribution is disclosing that this call blocks, which annotations cannot convey, plus the fact that a matched flow is handed back. However it says nothing about what happens when the required timeout_seconds expires, whether that is an error or an empty return, or whether consumption of the paused flow mutates state (annotations claim both readOnlyHint and destructiveHint true).
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?
A single sentence, front-loaded with the blocking behavior and ending with the routing hint. No filler, no restatement of the name.
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?
With no output schema, the description has to carry the return-value burden and only gestures at it ('return it for resume_breakpoint') without saying what identifying handle comes back. Combined with the unaddressed timeout outcome and the undescribed phase/url filters, a blocking, side-effect-flagged tool needs more.
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 coverage is only 67% and phase has an enum with no description at all, so the description needed to compensate and does not. It mentions no parameters: not the url pattern matching semantics, not the phase filter, and critically not what timeout_seconds expiring means for the caller.
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?
Names a specific verb and resource ('Block until one of your breakpoints pauses a flow') and immediately distinguishes itself from the related blocking sibling by naming the follow-up tool resume_breakpoint. An agent can tell it apart from wait_for_request and set_breakpoint without opening any schema.
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 implied workflow (set a breakpoint, then block here, then call resume_breakpoint) is clear from the wording, and it explicitly names resume_breakpoint as the next step. But it never states prerequisites (do breakpoints need to exist first?), or how this differs from wait_for_request, which is the obvious alternative an agent would weigh.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.