join_session

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

With no annotations, the description carries the full burden. It does disclose one important side effect — the joined session becomes the current one — which is not derivable from the schema. But it says nothing about auth/role requirements, what happens if the agent is already in a session, or what failure modes (invalid or expired code) look like.

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?

Two short sentences with zero filler; the identification methods are front-loaded and the state effect follows immediately. Nothing could be removed without losing information.

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 three-parameter tool with no output schema and no annotations, the description covers both input paths and the resulting state change. The remaining gap is the all-optional schema: it never states that exactly one of session_id or code must be supplied, leaving the agent to guess what an empty call does.

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 67%: 'code' documents the ABCD-EFGH format and 'server' documents its default, while session_id is undocumented in the schema — the description partially compensates by saying the id comes from list_projects. It does not clarify that code and session_id are alternative, presumably mutually exclusive inputs, which matters because no parameter is required.

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+resource ('Join a session') and names both supported identifier paths (session id or invitation code), plus the source of the id ('from list_projects'). It does not distinguish itself from the close sibling switch_session, so it falls short of a 5.

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 implies usage by pointing to list_projects as the origin of session ids, which gives the agent a concrete workflow entry point. However it never says when to join versus switch_session, open_project, or login, and gives no exclusions or prerequisites.

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