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

Annotations already cover readOnly/idempotent/openWorld safety, and the description adds real context beyond them: viral_tracks is daily-only and include_play_counts is slower. That 'slower' note and the default-to-latest behavior are the kind of operational detail annotations cannot express.

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 tight sentences: resource and chart types first, entry fields second, default last. No filler and no repetition of annotation-declared safety traits.

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 correctly spends its words describing the shape of each entry (rank, previous/peak rank, days/weeks, movement, streams). Defaults are covered; only edge behaviors such as out-of-range dates or empty results are unaddressed.

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; the description adds meaning by tying period to output units ('days (or weeks) on the chart') and noting streams are only present for top_tracks. That clarifies field semantics rather than repeating 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?

States a specific verb+resource ('Spotify Charts by country') and enumerates the four chart types it returns, which cleanly separates it from siblings like get_tracks or get_artist_overview. An agent can tell what this returns without opening the schema.

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?

Explains the default behavior ('defaults to the latest published daily chart') and flags the viral_tracks daily-only constraint, which guides selection among the chart enum values. It doesn't name alternative tools or state exclusions, but the chart-type mapping functions as implicit routing guidance.

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