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

Annotations already indicate this is a write operation (readOnlyHint=false, destructiveHint=false). The description adds useful behavioral context: it returns the monitor and, for heartbeats, the ping URL to call after each run. It also clarifies that page_id may be a shared page, which is beyond what annotations provide.

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, front-loads the core purpose, and packs the key distinctions (heartbeat vs HTTP, page placement, return value) without waste. Every sentence earns its place.

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 creation tool with 10 parameters and no output schema, the description covers the essential context: what it creates, the two modes, the page target, and the return value. It doesn't explain all parameter interactions, but the schema covers parameter details, and the description provides enough for an agent to select and invoke the tool correctly.

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 10 parameters. The description adds a little context by explaining the default behavior (first page) and the return value, but it doesn't add significant meaning beyond the schema's parameter descriptions. Baseline 3 is appropriate.

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 tool creates a monitor, distinguishes between heartbeat and HTTP check types, and specifies the target page. It uses a specific verb ('Create') with a clear resource ('monitor') and differentiates the two modes, which distinguishes it from siblings like get_monitor or list_monitors.

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 when to use this tool (to create a monitor) and provides context about the two kinds of monitors and the page placement. It doesn't explicitly state when not to use it or name alternatives, but the sibling list and the clear creation purpose make the usage context clear.

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