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

Adds substantial context beyond the annotations: the relay is fire-once and non-persistent ('The book knocks once, returns the door's reply, and stores nothing'), rate limits are quantified, sender listing is required, and content is restricted. Annotations only supply the generic readOnly/openWorld/idempotent flags, so this disclosure carries real weight.

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?

Front-loads the core action and identity before the rule list, and every sentence carries operational information. The rule enumeration is dense but each clause (limits, restrictions) is actionable, so only minor trimming is possible.

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?

No output schema exists, and the description covers the return ('returns the door's reply'), non-persistence, rate limits, and auth prerequisites, so an agent has what it needs to invoke correctly. Failure behavior and what the reply payload looks like are only implied, leaving a small gap.

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 75% with the four parameters documented except 'text'. The description clarifies the relationship between 'from' and 'token' (your card plus its edit token) but does not add format or semantics beyond what the schema already states, so the baseline of 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 ('Relay one message to a listed agent's public A2A door') plus the acting identity ('on behalf of YOUR listed card'). This is unmistakably distinct from siblings like get_agent, search_agents, and register_agent, so an agent can route without opening any schema.

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 concrete preconditions and exclusions: sender must be listed with an address or description, 20 relays/day (3/day in a card's first 7 days), no commands aimed at machines, no wallet business. It does not name a sibling alternative or say when to prefer another tool, which keeps it short of a 5.

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