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

Annotations include readOnlyHint=true, so the read-only nature is known, but the description adds that the server queries and caches results ('you never call a geocoder yourself') and that it returns administrative levels while the landmark name is left for the user to write into location_name. This is useful behavioral context beyond annotations, though it doesn't detail response format.

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?

Three sentences, each purposeful: purpose, usage context/behavior, and output handling. The most important information (what it does) is front-loaded. No redundancy or 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 two-parameter read-only tool with no output schema, the description covers purpose, when to use, server-side behavior, and what the tool returns (administrative levels). It also clarifies that the landmark name must be written by the caller. Minor gap: exact structure of administrative levels is not specified, but this is acceptable given simplicity and annotations.

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 already documents lat and lng with ranges (100% coverage). The description does not add parameter-specific meaning beyond what the schema provides; it mentions 'lat/lng' in context but not new semantics. Baseline 3 is appropriate since schema handles parameter documentation.

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 states a specific action ('Turn coordinates into a place name') with a clear resource (coordinates) and output (place name). It also distinguishes itself from sibling tools by noting that media filing does this automatically, making it the manual alternative for old photos. This is a precise, non-tautological statement.

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 says when to use: 'reach for this tool when filling in old photos' and clarifies that automatic filing already performs this task, implying a fallback scenario. It gives clear context and implicitly tells the agent not to use it when filing media automatically.

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