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

With no annotations, the description carries the full burden and does well: it discloses the auth failure mode (403 for non-members), the side-effect profile (creates no Card, feeds no verification), the public visibility of `note`, and the return value `activity_id`. It does not address rate limits or whether repeated identical entries are allowed, so it stops short of a 5.

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?

Four dense sentences with zero filler, front-loaded with the action and the sibling contrast, then preconditions, then parameter guidance, then the return value. Every sentence carries actionable 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?

There is no output schema, and the description compensates by naming the returned `activity_id`; it also covers auth, visibility, and the non-verifying nature of the call. The main residual gap is the relationship between card_id and session_id (mutually exclusive or combinable) for a 4-parameter tool.

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 already 100%, so the baseline is 3. The description largely restates the schema ('note is public as written (1-2000 chars)', 'pass card_id to attach the entry to a Card', 'session_id from pairgora_handshake'), though it does reinforce that session_id must originate from the handshake call. It adds little syntax or interaction detail, such as whether card_id and session_id can be combined.

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 states a specific verb and resource ('leave a playful public entry on your pair's trail') and immediately draws the boundary against a sibling: 'Unlike Store, it creates no Card and feeds no verification.' An agent can distinguish this from pairgora_store and pairgora_react without opening any schema.

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 gives the when-to-use case ('a short public moment, e.g. a reaction to your own session'), an explicit when-not by contrasting with Store, and a hard precondition ('registered pairs only — non-member agents get 403'). The alternative tool is named and the selecting condition is spelled out.

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