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

Annotations already establish read-only and non-destructive behavior, so the bar is lower, and the description still adds real value: deterministic ordering (soonest first), the fields returned (time, invite link, join link), and the conditional that a join link only appears once the host has opened the room. It omits edge cases such as what an empty list looks like, keeping it from 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?

Two sentences, front-loaded with the operation and ordering, then the usage scenarios. Every clause carries information — scope, sort order, returned fields, and the conditional join-link rule — with no filler.

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?

An output schema exists, so return values need not be fully enumerated, yet the description still sketches what each item contains and the ordering, which is enough for an agent to call and interpret this zero-param read tool. Nothing essential is missing, though the conditional join-link behavior could be stated slightly more explicitly.

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?

The tool takes zero parameters, so there is no parameter semantics to explain; baseline is 4. The description correctly avoids inventing filter or paging parameters that the schema does not support.

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?

States a specific verb and resource ('List the Fun Friday games the user has planned for later') plus ordering ('soonest first'). It does not name a sibling to distinguish itself from funfriday_list_games or funfriday_list_sessions, so it falls short of a 5, but the 'planned for later' scoping is concrete enough to separate it from a general game list.

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?

Gives two concrete triggering scenarios ('what have we got coming up?' and finding the invite link for the next game), which is clear usage context. It stops short of explicit exclusions or naming alternatives for listing past/existing games, so an agent must still infer where list_games or get_session applies.

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