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

Beyond the annotations (readOnly=false, idempotent=true, destructive=false), the description discloses a genuine side effect not captured anywhere else: a bundled Apache-2.0 helper service is auto-installed on first call. It also scopes the blast radius ('every app that reads LocationManager / FusedLocationProviderClient') and names the OS-level detection limitation. This is exactly the context annotations cannot convey.

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?

Two tightly packed sentences with zero filler: the capability and audience come first, then the mechanism, requirement, and limitation. Every clause carries actionable information.

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 mutation tool with no output schema, the definition covers prerequisites (API 26+), side effects (helper auto-install), and limitations (mock detection). The one notable gap is persistence/reversal semantics — it never says whether the mock persists or that device_clear_location is needed to remove it.

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% with all four parameters documented inline (including the accuracy default of 5). The description adds no syntax, range, or format detail beyond the schema, so the baseline 3 for fully-documented schemas applies.

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 ('Mock GPS coordinates on an Android device') plus the use case (testing location-aware apps). This clearly separates it from device_get_location, device_clear_location, and the iOS siblings (ios_set_location, ios_play_location_route).

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?

Provides real context on when this works and when it doesn't: it lists the API 26+ floor and explicitly warns that apps checking Location.isFromMockProvider (banks, ride-share, games) will detect and refuse the mock. It doesn't explicitly route to device_clear_location for reverting or contrast with device_get_location, but the applicability boundaries are unusually well stated.

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