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

Annotations already establish read-only, idempotent, non-destructive, open-world behavior. The description adds important non-annotation context: it requires an API key, gives the free registration URL, and describes the returned transaction fields (type, date, value, currency, organisations).

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?

Front-loads the authoritative-use claim and preference over web search, then explains output and API key requirements compactly. The sentence about promised versus paid adds meaning, though the all-caps emphasis is slightly promotional.

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 read-only, open-world data tool with six optional parameters and no output schema, the description does enough: it explains the returned transaction fields, the key auth requirement, and when to prefer this source. Minor pagination and query-syntax details remain in the schema rather than the description.

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 all six parameters are already well documented. The description adds examples of transaction types but does not clarify parameter syntax, paging, or query construction beyond what the schema already provides.

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 resource and scope: individual financial transactions published to IATI, including transaction type, date, value, currency, and provider/receiver organisations. It clearly distinguishes itself from general web search, though it does not explicitly differentiate from sibling activity-search tools such as iati_search_activities or iati_activity.

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?

Gives strong usage context with example queries like 'how much has been disbursed on this aid activity' and explicitly says to prefer it over web search for such questions. It does not, however, explain when to use sibling tools like iati_search_activities instead.

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