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

With destructiveHint=true and idempotentHint=true already declared, the description earns credit by clarifying that the change is stored only—"Nothing is sent now"—so the agent knows no live request fires, and by spelling out that null removes the saved body. It does not cover auth requirements or whether concurrent scheduled checks pick up the change mid-flight.

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?

Three short sentences, no filler, with the core action stated first and the two caveats (deferred use, null clearing) following. Every sentence carries information the agent needs.

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 two-parameter mutation with no output schema, the description covers purpose, applicability condition, side-effect scope, and null semantics. The one omission is what happens when body is omitted entirely (presumably unchanged), which the agent must infer.

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 100% and both parameters are documented in the schema, including the "null clears it" semantics, so the description's parameter content is largely a restatement. Baseline 3 applies: the description adds no syntax, size limits, or behavior for an omitted body parameter beyond what the schema already says.

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?

"Change the saved body of a monitor's uptime check" gives a specific verb plus a tightly scoped resource, distinguishing it in substance from headers/content/check-method updates. It never names those siblings, so differentiation depends on the agent parsing the noun phrase rather than on an explicit pointer.

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 does state the operative condition—the body is applied on scheduled checks whose method is POST, PUT, PATCH or QUERY—which implicitly tells the agent when the value matters. It offers no explicit guidance on when to choose this tool over the adjacent vs_monitors_update_request_headers or vs_monitors_update_content tools, and no prerequisite/permission context.

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