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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuinely non-derivable context: the card renders only in a compatible connected MCP Apps host, no MyLegend login is needed for public cards, and it should only be invoked once. It stops short of describing failure behavior when the host is incompatible or the slug is unresolvable.

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?

Tight and front-loaded: the invocation trigger comes first, followed by what renders, then exposure control and slug sourcing. Four sentences with minimal waste, though the slug-provenance sentence overlaps the schema.

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 read-only display tool with no output schema, the description covers the trigger, the rendered content, the host-compatibility constraint, the auth posture, and the call-once rule. Nothing an agent needs to invoke it correctly 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% with one parameter, so the schema already carries slug format, pattern, length and a provenance note. The description's slug guidance ('resolved slug from find_person or a known MyLegend profile URL') largely restates what the schema already says, so baseline 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?

States a specific verb and resource: it 'shows the card, with questions and a private message composer' for a person's MyLegend profile. It also distinguishes itself from siblings by naming ask_person (follow-up answers without another card) and find_person (slug resolution).

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?

Explicit trigger ('Use this when the user asks to see a person's MyLegend profile'), explicit de-duplication rule ('Invoke once to display the card'), and explicit routing to alternatives ('use ask_person for follow-up answers without another card'). Nothing about when to use or not use it is left to inference.

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