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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true, so the safety profile is covered. The description adds real behavioral value beyond that: it discloses the data-provenance fallback chain (live ADS-B → last fix → base) and that each position is returned with its source, which tells the agent how to interpret staleness. It omits freshness/rate-limit details, but the lineage disclosure is substantive.

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?

A single front-loaded sentence with zero filler. The em-dash fallback clause packs the most important semantic (definition of 'last-known') into the opening statement rather than burying it.

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?

An output schema exists, so return structure is covered, and annotations cover safety. Combined with a fully documented single parameter and a description that explains the position-source semantics and the no-live-data fallback, an agent has everything needed to call and interpret this tool.

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?

One parameter with 100% schema description coverage, so the schema already documents portfolio_id and its provenance (list_portfolios). The description adds nothing about the parameter; 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?

Names the resource (each aircraft in a portfolio) and the exact payload (last-known position plus its source), with a precise fallback hierarchy: live airborne, else last ADS-B fix, else base. This distinguishes it cleanly from siblings like get_portfolio_aircraft (roster) and get_tracked_aircraft_snapshots (tracking history) without the agent needing to open 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?

Usage is implied by the description — an agent can infer you call this to see where portfolio aircraft physically are — but there is no explicit when-to-use, when-not-to-use, or pointer to a sibling such as get_portfolio_aircraft or get_tracked_aircraft_snapshots. The prerequisite (portfolio_id from list_portfolios) lives only in the schema, not the description.

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