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

The annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered; the description goes beyond them by disclosing the auth requirement ('user's Cotlet API key with access to this app') and describing what the read returns (RSVP answers plus which emails were sent). It omits rate limits or latency, but adds genuine context atop the 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?

Purpose is front-loaded, but the second sentence ('Returns one guest with the full set of RSVP answers and which emails were sent to them') largely restates the first sentence's 'all RSVP answers and email tracking history,' so the text is not fully free of redundancy.

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?

With no output schema and no param ambiguity, the description carries the burden of explaining return content, which it does (contact details, party, tags, RSVP answers, email history), and it adds the auth requirement. What an agent needs to call it correctly is present; only the explicit sibling routing is missing.

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% and both parameters (event_id 'from list_events', guest_id 'from list_guests') are fully documented in the schema. The description adds no format, syntax, or sourcing detail for either parameter beyond what the schema already provides, so the baseline of 3 applies.

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 gives a specific verb+resource ('One guest profile') and enumerates the returned fields (contact details, party, tags, RSVP answers, email tracking history). The 'one guest' scoping implicitly separates it from joy_list_guests and joy_get_rsvp_summary, though it never names those siblings explicitly to remove all doubt.

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 supplies a concrete workflow trigger: 'Use it before changing an RSVP or contacting the guest,' which tells the agent when to reach for it. It stops short of naming alternatives (e.g., use list_guests to find the id in the first place) or stating when NOT to use it, so it is clear context rather than full routing guidance.

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