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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so the safety profile is fully covered elsewhere. The description adds only the 'real-time' framing, with no detail on update cadence, staleness, or rate limits. Adequate but thin beyond 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?

A single front-loaded sentence naming the resource, the data freshness, and the filter in that order. Nothing is redundant and nothing is padded.

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-value shape need not be described, and the tool has only one optional parameter. What remains is a clear, if minimal, definition for a simple read-only lookup; only the lack of sibling routing keeps it from being fully complete.

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% and the single routeId parameter is fully documented in the schema, so the baseline is 3. The description's mention of an optional route filter matches the schema without adding format, syntax, or fallback detail (e.g., case sensitivity or invalid-route behavior).

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 and resource ('Get real-time positions of DC Metro buses') with a clear scope and an optional filter. It implicitly distinguishes itself from get_train_positions and get_vehicle_positions via the 'bus' mode, but never names those siblings explicitly, so the differentiation is inferential rather than stated.

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 phrase 'optionally filtered by route' implies usage context (omit the filter for the full fleet), but there is no explicit when-to-use guidance, no exclusions, and no routing to alternatives such as get_bus_predictions or get_vehicle_positions. Usage is implied rather than directed.

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