session_back

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It mentions the session_start prerequisite but does not explain what the tool returns, how far back it goes, whether it mutates navigation state, or what happens at the beginning of history.

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 very short and front-loaded, with no wasted words. It earns its place by conveying purpose and a prerequisite, though it could expand slightly on behavior without becoming verbose.

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 single-parameter tool with no annotations and no parameter explanation, this description is insufficient. It correctly identifies the purpose and prerequisite but leaves the tool's behavior and max_chars semantics unexplained, making confident invocation difficult.

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 only parameter, max_chars, has 0% schema description coverage and is not mentioned in the description. The agent cannot infer what max_chars controls, such as output truncation or result size, which is essential for correct invocation.

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 action: navigate backward through the session tab history. It uses a specific verb ('back') with a clear resource ('session tab history') and distinguishes itself from sibling navigation tools like session_navigate or browser_navigate.

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 states a prerequisite: 'Requires session_start.' This gives useful context about when it can be used, but it does not mention when not to use it or compare it to alternatives such as browser_navigate or session_navigate.

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