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

Annotations already declare a safe read (readOnlyHint=true, destructiveHint=false), and the description goes well beyond them: it discloses the '(extension)' second-facility convention, the otherSitesInCity field on city-name lookups, candidate-return behavior for partial names instead of guessing, and the caveat that coordinates are city-centre rather than facility address. That is substantive behavioral context an agent could not infer from the schema.

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-loaded with the return payload, then usage routing, then edge cases. Every sentence carries distinct information; the enumeration of returned fields is dense but justified given there is no output schema.

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?

With no output schema, the description compensates by naming the content categories returned and the special fields (Looking Glass node id, otherSitesInCity). Combined with the 100%-covered input schema and safety annotations, an agent has everything needed to call it correctly and interpret the result.

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 100%, so the baseline is 3, but the description adds meaning the schema does not: how a bare city name is resolved (primary site in full, others named in otherSitesInCity), and that a partial match yields candidates rather than an arbitrary pick. These are real semantics for the single 'location' parameter beyond the slug/city format already documented in the schema.

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?

Opens with a specific verb+resource and enumerates exactly what is returned (building specs, compliance, security, connectivity, power, Looking Glass node id, FAQs, URL). It is immediately distinguishable from list_data_centers and find_nearest_data_centers, which are named as the discovery alternatives.

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 states the trigger condition ('Use it once the site is known') and routes to the correct siblings for discovery ('to find sites, use list_data_centers or find_nearest_data_centers'). It also documents disambiguation behavior for ambiguous input, which is a usage concern rather than a schema one.

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