session.open_existing

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

With no annotations, the description must fully disclose behavioral traits, but it only states a high-level action. It does not explain whether the tool modifies state, requires permissions, or has side effects. It also fails to mention how parameters like read_only, deterministic, or update_analysis affect behavior.

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 extremely concise at one sentence, but this brevity sacrifices essential information. It is not well-structured for an agent because it lacks any breakdown of parameters or behavior. While it avoids fluff, it does not earn its place since it fails to explain the tool adequately.

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 has 5 parameters, no output schema, and no annotations, the description is severely incomplete. It does not address prerequisites, return values, or how the tool integrates with the session lifecycle. A tool opening a session from a file should clarify if it replaces the current session or loads a snapshot, but none of this is mentioned.

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 0%, and the description adds no meaning to any of the 5 parameters. The only implicit link is 'from an existing session's file' hinting at source_session_id, but there is no explanation of options, read_only, deterministic, or update_analysis. The description provides virtually no semantic value beyond the raw parameter names.

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 ('Open another session') and the source ('from an existing session's file'). This distinguishes it from siblings like session.open (which likely opens a new empty session) and session.open_bytes (which opens from byte data). The verb 'open' is somewhat generic but adequate given the context.

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?

No guidance is provided on when to use this tool versus alternatives such as session.open or session.open_bytes. There are no explicit when-to-use or when-not-to-use instructions, making it difficult for an agent to decide correctly without additional context.

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