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

Discloses the single most surprising behavioral trait — W3C Element Send Keys APPENDS and does not clear, so repeat calls concatenate — which no annotation conveys. It also enumerates failure modes: element not editable, and stale element after navigation, with the recovery step.

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?

Dense and front-loaded: the append caveat follows immediately after the core action, and remedy plus error conditions come last. Slightly long, but nearly every clause carries decision-relevant information; the parenthetical alternatives could be trimmed.

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 3-parameter mutating session tool with no output schema and no annotation coverage of semantics, the description covers action, side effects, workaround, session coupling, cross-platform scope, and error recovery. Nothing an agent needs to invoke it correctly is missing.

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%, so baseline is 3, but the description adds real constraints beyond the schema: sessionId must be the session that found the element, and elementId refers to an element whose editability and staleness affect success. Only the 'text' parameter gets no extra treatment.

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 ('Type text into an element') and pins the element identity to the sibling producer session_find_element via elementId. An agent can distinguish it from session_click, session_execute and session_find_element without opening schemas.

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?

Explicitly tells when to use it (typing into an element already located by session_find_element), the condition that changes the approach (replace vs append), and names the alternative tool for clearing (session_execute setting value to an empty string). Nothing about choosing between siblings is left to inference.

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