join_interest

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

With no annotations provided, the description carries the full behavioral burden. It discloses the feed-population effect and the active-versus-emerging eligibility rule, which is meaningful. However, it does not mention auth requirements, idempotency, failure modes, reversibility via leave_interest, or what the operation returns.

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?

Three short sentences, each earning its place: the action, the real-world effect on the feed, and the key eligibility constraint with the correct sibling tool. No filler or redundant restatement.

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 two-parameter tool with no output schema, the description covers the essential context: what joining does, why it matters, and which kind of interest is eligible. Minor omissions like response shape or already-joined behavior are not critical to correct invocation.

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 100%, so the schema already fully documents token and interest_id. The description adds context about active versus emerging interests, which indirectly clarifies what values of interest_id are valid, but it does not substantially extend the parameter semantics beyond the schema.

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 opens with a specific verb and resource: "Join an interest area." It also distinguishes itself from sibling tools by explicitly naming endorse_interest as the alternative for emerging interests, so an agent can tell them apart immediately.

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?

It states the primary purpose (populates the catch_up feed) and gives an explicit conditional: only active interests can be joined, while emerging ones are endorsed instead via endorse_interest. This is direct, actionable routing guidance with a named alternative.

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