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

Adds real context beyond annotations: it discloses the quota cost ('spends one autocomplete request from the monthly plan allowance') and the side effect of persisting the observation, which explains why readOnlyHint=false despite being a lookup. Nothing on error behavior or failure modes, but the cost/persistence disclosure is the key non-obvious trait.

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 sentences, zero waste, with the core function and result ordering front-loaded and the cost/side-effect note trailing. Nothing repeats the title or schema verbatim.

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 4-parameter, fully documented schema with no output schema, the description covers purpose, result ordering, quota cost, and persistence. Only the output shape (what a suggestion record looks like) is unaddressed, which is minor for a simple list-returning tool.

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%, so all four parameters are already documented including the GOOGLE_PLAY_SOURCE requirement and the country/language examples. The description adds only conceptual framing ('what the shopper has typed so far', result ordering) rather than new per-parameter meaning, so baseline 3 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+resource (live store search suggestions for a prefix) and names both upstream sources (Apple search hints / Google Play suggest), which pins down the behavior precisely. It implicitly distinguishes itself from list_autocomplete_history by emphasizing 'live' and from search_store by being prefix-based, but doesn't name those siblings explicitly.

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?

Usage is only implied: the agent can infer this is for live suggestion lookup rather than full app search or stored history, but there is no explicit 'use this when' or exclusion against search_store / list_autocomplete_history. The Google Play source prerequisite sits in the schema rather than the description.

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