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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds genuinely new behavior: org isolation returns 404 never 403 ('another org's fan-out never even appears to exist'), the verify view recomputes rollup_ref server-side and reports ok/mismatches, and no dispatch permission is required (read tier). These are meaningful traits beyond the structured hints.

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?

Dense but front-loaded: the core action and its view selector come first, then per-view detail, then the security/permission notes. Sentences are information-packed, though the view=verify sentence is long and the whole block is heavier than a single-purpose read tool strictly needs.

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 carries the return-value burden and does so view by view, including which fields appear (seat counts, spend, cap, poll_after_s; leaf path/sha256/completion_id). It also covers the auth/permission model and org-isolation edge case, leaving no obvious gap for correct invocation.

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% and the schema's enum description is terse ('status (default), report, rollup or verify.'), so the description meaningfully expands it by explaining what each view actually returns (state/counts/cap/synth_deadline_at/poll_after_s vs. leaves with path/sha256/completion_id). The fanout_id param is only restated as the T_F root UUID, so it stops short of a 5.

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+resource (read a fan-out by id) and immediately scopes it with the four view modes, so the agent knows exactly what it retrieves. It also distinguishes itself from the related get_cycle_report by noting view=report returns that report inline, rather than leaving the agent to guess which sibling to call.

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 explicit per-view selection guidance (status for state/counts, report for the full cycle, rollup for the response_value plus leaves, verify for recomputation) and a notable caveat: verify is 'a convenience, not a substitute' for scripts/verify-fanout.js. No explicit 'when not to use this tool' against a named sibling alternative, 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.