get_mutual_guests

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

Annotations already establish the safety profile (readOnlyHint, idempotentHint, destructiveHint false). The description adds meaningful behavioral insight by defining what 'mutual guests' means (people invited to this event who you're also connected to elsewhere), which is beyond annotation coverage. It doesn't mention pagination or edge cases, but the output schema and annotations cover the essentials.

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 two sentences with zero waste. The first sentence states the primary purpose and defines mutual, the second explicitly differentiates from siblings. All content earns its place and is front-loaded for quick comprehension.

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 this simple read-only list tool with two well-documented parameters, an output schema, and rich annotations, the description fully captures the purpose, scope, and relationship to nearby tools. Nothing critical 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 descriptions cover 100% of the parameters: event_id is described as 'The Partiful event ID' and fields are fully listed with dot-path semantics. Since the schema already provides clear parameter meaning, the description adds no additional parameter-level detail, warranting the baseline score of 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 ('Get') and clearly defines the resource: 'guests you have in common with a specific Partiful event.' It also explicitly distinguishes the tool from two key siblings (get_guests and get_mutuals), making its purpose unambiguous.

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 explicitly states when to use this tool by contrasting it with alternatives: 'Distinct from get_guests (every guest, not just mutual ones) and get_mutuals (your mutual connections generally, not scoped to one event).' This provides clear exclusions and context for selecting this tool.

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