repl_list_sessions

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds context beyond those by specifying the return format (JSON array) and contents (IDs, timestamps, variable counts) and that only active sessions are listed. This provides useful behavioral detail not present in the schema or annotations.

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: two sentences pack the purpose and the return structure. It is front-loaded with the core action and immediately provides the expected output. No filler or repetition of schema/annotations.

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 simple, parameterless list operation with a rich annotation set and an output schema, the description fully conveys what the tool does and what it returns. It is complete enough for an agent to select and invoke it without missing critical details.

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 tool has zero parameters, and the schema is empty. A baseline of 4 is appropriate for no-parameter tools because there is nothing to document. The description does not attempt to add parameter semantics, correctly avoiding redundancy.

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 uses the specific verb 'List' and clearly identifies the resource as 'all active REPL sessions.' This distinguishes it from sibling tools like repl_delete_session (which removes sessions) and repl_get_variable (which retrieves specific variables within a session).

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 clearly implies when to use this tool: to see all active sessions. However, it provides no explicit guidance on when NOT to use it or which alternative to choose for related tasks (e.g., repl_list_namespace for namespaces). The usage context is implied rather than stated.

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