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

Annotations already indicate readOnly, idempotent, non-destructive. The description adds valuable context: data freshness (served from storage, never recomputed), the error handling for unowned snapshots (not found vs forbidden), and the auth requirement. These details go beyond annotations without contradicting them.

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?

The description is concise, front-loaded with the purpose, then adds behavioral notes in a logical order. Every sentence adds value without redundancy or filler.

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?

For a single-parameter get-by-id tool with no output schema, the description covers what is returned, freshness semantics, error behavior, and auth requirements. No critical information for invoking it correctly is missing.

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?

The single parameter snapshot_id is fully described in the schema (coverage 100%) with its own description pointing to list_portfolio_snapshots. The tool description adds no extra meaning beyond the schema, so it meets the baseline but doesn't elevate it.

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 verb (Fetch), a resource (portfolio snapshot), and enumerates the exact fields returned (label, schema version, rollup payload, content hash, recorder, timestamp). It also contrasts with list_portfolio_snapshots and diff_portfolio_snapshots by focusing on a single snapshot, making it unambiguous.

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?

The description explains when to use it: to retrieve the exact stored snapshot, explicitly noting it is never recomputed from live tickets. It also mentions that unowned snapshots return not found rather than forbidden, and requires authentication with tickets:read scope. It does not explicitly name alternative tools for live data, but the behavior statement implies the distinction.

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