User Traits

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

Annotations already carry the safety profile (readOnlyHint=true, idempotentHint=true, destructiveHint=false), so the description need not restate it. It adds genuine behavioral information beyond annotations: the mode-dependent default selection logic and case-insensitive matching for the 'users' mode. No statement contradicts 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?

Three sentences in about 40 words, with the core purpose front-loaded and each mode explained in its own clause. There is no filler, no repetition of schema text, and every sentence earns its place by clarifying behavior.

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 mode-polymorphic tool with five parameters and no output schema, the description covers all invocation variants and their parameter requirements, which is the main risk an agent faces. It stops short of describing the return shape or limits/offset behavior, but annotations cover the safety profile and the mode semantics are fully specified, leaving no ambiguity about how to call it correctly.

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 coverage is 100%, so the schema already documents every parameter including the mode defaults and required conditions for key and value. The description adds modest value beyond the schema — chiefly the case-insensitive matching detail and a readable consolidation of mode-to-parameter interplay — but does not substantially extend what structured fields already convey.

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 ('Get user trait keys, values, or find users by trait') and fully disambiguates the tool's polymorphic behavior across three named modes. Because it is framed around user traits, it is clearly distinct from siblings like rybbit_get_user and rybbit_list_users, which target the user record itself rather than trait metadata.

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 gives explicit conditional usage guidance for mode selection ('mode=values (default when key is provided)', 'mode=keys' default otherwise), so an agent knows which invocation variant applies in which situation. It does not name alternatives or exclusion criteria among the tight siblings, but the mode-level routing is clear and actionable.

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