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

Annotations cover the safety profile (readOnlyHint true, openWorldHint true), and the description adds two things beyond them: an auth requirement ('Needs your key') and an enumeration of what the response contains. Since no output schema exists, disclosing the returned fields is genuinely useful behavioral context. It doesn't cover rate limits or error behavior, but for a read-only aggregate that is a minor gap.

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 response contents, and every clause maps to a real field the caller receives. The long enumeration is dense but each item is informative given the absent output 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?

With no output schema, the description compensates by listing the summary components an agent will receive, and it states the auth need and the intended session-start use. What remains unstated (response shape, whether counts are truncated or paginated) is minor for an aggregate overview endpoint.

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% for the single api_key parameter, so the schema already explains its fallback role relative to an Authorization header. The description only echoes 'Needs your key', adding no format or precedence detail beyond the schema. Baseline 3 applies when the schema does the work.

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 names the specific resource (an account summary) and enumerates its contents: status, limits, unread notification count, replies in the last 3 days, current notice and hot posts. This is far more specific than the ambiguous tool name 'home' and signals it is an aggregate dashboard rather than a single-purpose endpoint. It stops short of explicitly distinguishing itself from overlapping siblings like notifications or get_notice, which an agent might otherwise confuse with the unread-count/notice parts.

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?

'Typically the first call when resuming with an existing key' gives a clear usage context that no sibling tool offers. There is no explicit when-not or named alternative, but the entry-point framing is sufficient to route an agent at session start.

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