Select active character

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

Annotations only declare idempotentHint=true; the description adds real value by disclosing the global side effect (affects all character tools) and repeat-call safety is implied by idempotency. It omits behavior on lookup failure, ambiguous partial-name matches, and whether selection persists across sessions.

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 effect and followed by accepted input forms; nothing is redundant or padded.

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 single-parameter, non-destructive context-setting tool with no output schema, this covers purpose, input forms, and blast radius. Only failure modes (unknown or ambiguous character) are left undiscussed.

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 baseline would be 3, but the description adds meaning beyond the schema's 'Character name or id' by stating that a unique *part* of the name is accepted — a fuzzy-match rule an agent could not infer from the schema. The 'unique' qualifier also hints at ambiguity resolution.

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 (makes default) and resource scope ('all character tools'), which distinguishes it from character_login and character_logout by describing the effect rather than an auth action. It never explicitly says 'do this after login instead of character_login', so sibling differentiation is implied rather than stated.

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?

'Makes a logged-in character the default' implies a prerequisite (must be logged in) and an ordering (use before other character tools), which is useful context. However, it gives no explicit when-not guidance and never names character_login or characters_list as alternatives for discovering or authenticating a character.

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