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

Annotations already declare readOnly, idempotent, non-destructive, so safety is covered. The description adds genuine behavioral value: the source is the Monetary Committee's own published decisions rather than a bare currentInterest snapshot, and it discloses the returned fields including effective_since history, nextInterestDate and lastPublishedDate.

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 core definition and scope first, then supporting detail about returned fields and data source. It is longer than strictly necessary — the parenthetical about currentInterest's snapshot is verbose — but each clause carries real meaning.

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?

No output schema exists, so the description must explain return values and it does: rate, effective_since, previous rate and its effective date, decision history, nextInterestDate, lastPublishedDate. Combined with annotations covering the safety profile and the no-parameter schema, an agent has everything needed.

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?

With zero parameters the baseline is 4, and the description cannot add param meaning beyond that. It does compensate somewhat by enumerating the fields the tool surfaces, which is information the empty schema does not carry.

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 — the current BOI policy interest rate — and explicitly narrows scope to Israel only. That scope statement also implicitly separates it from the boi_exchange_rate / boi_exchange_rates siblings, which cover FX rates rather than the policy rate.

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 clear usage context: it is the Monetary Committee benchmark rate in % per annum for Israel only, and notes it includes decision history plus nextInterestDate. It never explicitly names when to prefer it over a sibling or what it should not be used for, so it falls short of a 5.

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