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

The annotations already establish read-only, idempotent, open-world, and non-destructive behavior, so the description does not need to repeat those traits. It adds useful behavioral context by disclosing the cost (1 credit) and the default series, though it does not describe return format or date-range behavior.

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 a single tight sentence with the most useful details front-loaded: the data source, example series codes, default, and cost. There is no 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 simple three-parameter read-only data retrieval tool with full schema coverage and rich annotations, the description supplies enough to make a correct common call. The main remaining gap is that it says "and more" without explaining how to discover other valid series codes or what the returned data looks like.

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%, so the baseline is 3. The description goes beyond the schema by mapping the generic series parameter to specific Bank of England codes and identifying IUDBEDR as the default, which helps an agent populate that parameter correctly.

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 clearly identifies the resource as Bank of England database series and gives concrete example series codes (IUDBEDR, XUDLUSS, IUMBV34), including the default. It stops short of an explicit verb like "fetch" and does not directly distinguish the tool from sibling rate/data tools such as fx_rates or world_bank.

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 Bank of England framing, the named series examples, and the stated default series. However, there is no explicit when-to-use or when-not-to-use guidance versus alternatives like fx_rates, hmrc_exchange_rates, or world_bank.

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