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

Annotations already declare this is read-only, open-world, idempotent, and non-destructive, so the safety profile is covered. The description adds useful behavioral context: the result is authoritative agency-code data and should be called before dependent tools, though it does not discuss auth or rate limits beyond the schema's _apiKey note.

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 compact and front-loads the data scope before ending with the actionable 'call this first' instruction. Every sentence earns its place with no redundant restatement of the title.

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 simple lookup tool with one optional credential parameter, strong annotations, and no output schema, the description supplies enough: it states the population returned, the key output concept (short agency code), and the intended first-call ordering.

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?

There is one optional _apiKey parameter, and schema description coverage is 100%, so the schema already explains it. The description adds no parameter-level meaning, but the schema is doing the heavy lifting as expected with full coverage.

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 resource and verb-like outcome: every Bay Area 511 transit operator with its short agency code. It names concrete examples (BART, Muni, Caltrain, etc.) and explicitly distinguishes the tool from sibling bay511 tools by saying they consume the codes returned here.

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?

It gives an explicit routing instruction: 'AUTHORITATIVE for which Bay Area agency code do I use; call this first.' That tells the agent both the use case and its precedence relative to the other Bay 511 tools.

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