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

Annotations already indicate readOnlyHint=false and destructiveHint=false, so mutation is communicated. The description adds behavioral context beyond annotations: the watch runs on a schedule, notifies upon changes, captures a baseline immediately, and returns JSON. It doesn't contradict annotations. It lacks details on cost or lifecycle but provides useful transparency for a mutation tool.

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 four sentences: usage trigger, exclusion with alternative, core function with details, and return format. It is front-loaded, each sentence adds distinct value, and there is no filler or repetition.

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?

Given the tool's complexity (10 params, nested object, no output schema), the description adequately covers purpose, usage, a concise explanation of diff modes (visual/text/both), and the return type. It doesn't explain lifecycle costs, but those are documented in parameter descriptions (e.g., paused, plan floors). The description is sufficient 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?

The input schema has 100% description coverage for all 10 parameters, including detailed semantics for fields like 'paused', 'diffMode', 'threshold', and the nested 'renderParams'. The description itself adds minimal parameter guidance, only mentioning that an active watch captures a baseline. Since the schema is comprehensive, a baseline of 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's purpose: 'Creates a Rendex Watch — monitors a URL on a schedule and notifies when it changes'. It also differentiates from sibling tools with the explicit directive: 'Do NOT use for a one-time capture (use rendex_screenshot)'. This is a specific verb+resource with clear scope.

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 explicit usage context: 'Use this when the user asks to monitor, watch, or track a webpage for changes, or to be alerted/notified when a page changes' and an explicit exclusion with an alternative tool: 'Do NOT use for a one-time capture (use rendex_screenshot)'. It also notes the baseline capture behavior, giving actionable guidance.

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