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

Annotations provide the safety profile (readOnlyHint=false, openWorldHint=false, destructiveHint=false), so the bar is lowered. The description still adds real context beyond them: it names the three deliverable events, defines the omit-events default, and clarifies that an empty URL stops delivery — behavior the agent could not infer from annotations alone.

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, front-loaded with the core action and the exact events, followed by default and stop behavior. No filler, no redundancy across sentences.

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 setter with no output schema, the description covers the deliverable events, the default, and the stop case, which is what an agent needs to call it correctly. It is slightly thin on replacement semantics (whether setting a URL overwrites a prior subscription), which keeps it from a 5.

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 both parameters and their empty/omit semantics. The description's statements about events and webhook_url largely restate what the schema descriptions say, adding no syntax or format detail beyond them. Baseline 3 applies when the schema does the heavy lifting.

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 and resource — sets the webhook URL that receives call.started, call.ended, and speak.completed for this seat — and enumerates the exact event names. No sibling tool covers webhook subscription, so there is nothing to disambiguate against, and an agent can identify the operation immediately.

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 operational conditions (omitting events receives all three; an empty webhook_url stops delivery) but never states when to reach for this tool versus any alternative. With no competing sibling, usage is implied rather than contradictory, which fits a 3.

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