Get an ETA proxy for a location (ZIP or city).
eta_minutes is null — HireLocksmiths does not pre-list ETAs. The tool returns the
number of vetted providers nearby and whether 24/7 emergency coverage exists (usually
fastest). For a real ETA, call request_quote and the locksmith confirms it directly.
Never invent a number of minutes.
| Name | Required | Description | Default |
|---|---|---|---|
| location | Yes |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), and the description adds genuinely new behavioral facts: eta_minutes is always null, the response carries a count of vetted providers and a 24/7 coverage flag, and it explicitly warns 'Never invent a number of minutes.' That is high-value disclosure beyond structured fields.
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?
Four short statements, front-loaded with the purpose, then the null-ETA caveat, then the return shape, then the alternative and the anti-hallucination rule. No sentence is 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?
There is no output schema, so the description must carry return-value meaning, and it does: what eta_minutes is, what the tool actually returns, and where to get a real ETA. For a one-parameter read-only lookup, nothing an agent needs to call it correctly is missing.
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 coverage is 0% and the single 'location' parameter has no schema description, so the description must compensate. It does so by defining accepted formats ('ZIP or city'), which is the key semantic for the only parameter, though it adds nothing about validation or failure modes for an unrecognized location.
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?
Names a specific verb and resource ('Get an ETA proxy for a location') and clarifies the input format (ZIP or city), which is more than the name alone conveys. It also differentiates itself from the sibling request_quote by explaining that real ETAs come from there, though 'ETA proxy' remains an odd framing that the rest of the text has to walk back.
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?
Explicitly routes the agent: use this for the proxy signal, but 'For a real ETA, call request_quote and the locksmith confirms it directly.' That names the alternative and the condition that selects it, which is exactly the when/when-not guidance an agent needs.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.