set_breakpoint

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

With no annotations provided, the description carries full burden. It discloses that breakpoints can be set preemptively before sessions start, which is useful behavioral context. However, it lacks details on permissions needed, error conditions, or what happens if a breakpoint already exists at that location.

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 description is two sentences with zero waste: the first sentence states purpose and supported types, the second provides crucial timing context. Every word earns its place, and key information is front-loaded.

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 and no output schema, the description is reasonably complete—it explains what the tool does, when to use it, and behavioral timing. However, it could better address error cases or interaction with sibling tools like 'list_breakpoints' or 'remove_breakpoint'.

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 100%, so the schema already documents all 6 parameters thoroughly. The description adds no additional parameter semantics beyond what's in the schema, meeting the baseline of 3 for high schema coverage.

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 clearly states the specific action ('Set a breakpoint'), target resource ('in PHP code'), and scope ('line breakpoints and conditional breakpoints with hit counts'), distinguishing it from sibling tools like 'set_call_breakpoint' or 'set_exception_breakpoint' by focusing on line-based breakpoints.

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 provides clear context about when to use it ('Can be set before a debug session starts - breakpoints will be applied when a session connects'), but does not explicitly mention when not to use it or name alternatives like 'update_breakpoint' for modifying existing breakpoints.

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