project_join

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

Annotations already disclose readOnly=false, idempotent=true, destructive=false. The description adds that this is a join operation with explicit session identity and that the response is a compact status with map recovery, which is some behavior beyond annotations. However, it does not explain side effects such as session creation or state transitions, and idempotentHint=true is not contradicted. With annotations present, this is adequate but not rich.

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 one sentence, front-loads the core action, and carries useful information without unnecessary words. It is concise and readable, though it packs several concepts compactly.

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 schema is rich with required fields and defaults, and there is no output schema, the description explains the response kind ('compact status with map recovery') but not the meaning of the required fields, the semantics of take_over_from, or the implications of joining with a parent session. It is adequate for a simple join call, but it leaves behavioral details to the caller's context.

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%, so the description is the only textual source for parameter meaning. The description mentions 'explicit session identity' (external_session_id), 'optional parent' (parent_session_id), and 'compact status' (response), but the remaining parameters like take_over_from, effort, request_id, repository, vendor, runtime, and model are not described. A 0% coverage baseline would expect the description to compensate; partial compensation merits a 3.

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 a specific verb ('Join') with a resource ('project') and mentions key modifiers (explicit session identity, optional parent) that distinguish it from a plain project query. It does not explicitly name siblings, but it conveys a session-joining behavior. The return phrase 'compact status with map recovery' adds some specificity.

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 a session/identity-joining scenario, and sibling names like project_status, work_claim, work_update suggest alternatives, but it offers no explicit when-to-use or when-not-to-use guidance. The phrase 'optional parent' hints at when to use parent_session_id, but no exclusions or alternative tool routing is given.

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