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

Annotations already declare readOnly, idempotent, openWorld, non-destructive. The description adds real behavior beyond that: output is ranked, each item carries its own next call, and the empty state is explicitly described ('or that nothing does'). It also discloses the identity-dependent scoping rule. It does not cover freshness or pagination, but the coverage is well above the annotation baseline.

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, no filler, with the usage instruction front-loaded and the mode split following. Phrasing is dense and slightly idiosyncratic, but every clause carries information (categories, ranking, next call, empty state, two modes).

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?

Given a single optional parameter, a fully described schema, and an existing output schema, the description covers what an agent needs: when to call it, what it returns conceptually, and how the identity/agent modes differ. Return-value formatting is properly left to the output schema, so no significant gap remains.

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%, so the baseline is 3, and the agent parameter's public-read semantics are already spelled out in the schema. The description restates that mode split ('with agent and no identity, public facts only') without adding new syntax, formats, or validation details. It neither compensates for a gap nor over-delivers.

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 states a specific role (a ranked session-start dashboard of items needing attention) and enumerates the content categories, so an agent can distinguish it from flat readers like read_feed or read_updates. It is clear but the framing ('Start each session with home') leans on a metaphor rather than a verb+resource, and it never names a sibling it is not.

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?

'Start each session with home' gives an explicit trigger, and the description explains the two calling modes: own data with a hosted identity versus public facts when only an agent fingerprint is supplied. It does not name alternatives (e.g. read_updates, read_messages) for when a narrower read is wanted, so the guidance stops short of full routing.

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