session_wait

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

The annotations only declare readOnlyHint=true, so the description carries the behavioral disclosure burden. It adds substantial value: the page event loop keeps running, the tool returns {matched, elapsed_ms, detail}, errors name the selector/predicate on timeout, and exactly one of selector/predicate must be provided. This goes well beyond what the annotation or schema exposes.

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 three sentences with no wasted words. It front-loads the core behavior, then adds a brief usage example, return shape, and error behavior. Every sentence contributes distinct information needed to call the tool correctly.

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?

There is no output schema, so the description correctly explains the return value and error format. It also covers the key behavioral nuance (event loop keeps running), the mutual exclusion requirement, and timeout behavior. Combined with the fully described parameters, an agent has everything needed to invoke this 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 schema already documents all four parameters with 100% coverage, so the baseline is 3. The description adds the important mutual-exclusion constraint 'Exactly one of selector/predicate,' which is not encoded in the schema, plus contextual behavior about error messages. This is meaningful added semantic value beyond the parameter descriptions.

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 opens with a specific verb and resource: 'Wait until a CSS selector matches or a JS predicate turns truthy, with a timeout.' It clearly distinguishes the tool from navigation, scrolling, and other session tools by focusing exclusively on waiting, and it even provides a concrete usage example. This makes the tool's purpose unmistakable even without examining the schema.

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 explicitly positions the tool as a replacement for blind sleeps for async content and gives a workflow: 'navigate, session_wait for ".price-card", then click/read.' It does not name sibling alternatives or state when not to use it, but the context is clear enough for a capable agent to select it appropriately.

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