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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds real value beyond them: the return shape (one row per person per connected account with handle, unread count, last message) and the auth requirement (inbox access via a key or an allowed connection).

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 purpose (recent conversations, newest first), then row shape, then usage, then auth. Each sentence earns its place, though the final access sentence is slightly dense. Overall well-sized for a 3-param list tool.

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, yet the description compensates by describing the returned row contents, and it covers ordering, default filtering behavior, and the auth prerequisite. An agent has everything needed to call it correctly.

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 the baseline is 3, but the description adds meaning: unread_only is framed as 'conversations waiting for an answer' and profile_id is tied to the per-connected-account row concept. It goes beyond the terse schema descriptions.

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 (list) and resource (inbox conversations/threads) with scope ('most recent... newest first') and describes the row shape. It names the sibling sprkly_get_inbox_thread and clarifies the relationship, so an agent can distinguish it from the read-one tool without opening a 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 clear usage context: pass unread_only to see conversations waiting for an answer, and use profile_id/person_id from a row with sprkly_get_inbox_thread to read a thread. This routes the agent to the right sibling. It lacks an explicit 'do not use when...' exclusion, so it falls just 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.