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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safe/read-only profile is covered by annotations. The description adds valuable behavioral context: the response is downsampled to the requested window and is byte-identical to a specific GET endpoint, including cost. This goes beyond what annotations provide.

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 earning its place: what it returns, how it behaves (downsampled, trend line), and operational facts (cost, byte-identical endpoint). Front-loaded with the core purpose.

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 read-only, idempotent historical-data tool with an output schema present, the description is complete. It covers the trend-line behavior, windowing, cost, and REST equivalence. Nothing needed to call it correctly is missing.

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% for two params, so baseline is 3. The description adds meaning by explaining that 'days' controls the downsampled window and that 'chain' uses DefiLlama naming; the cost disclosure adds operational semantics. However, the description doesn't elaborate on allowed chain names or date formatting, so it earns a 4 rather than 5.

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?

Description states a specific verb+resource: 'Daily total-value-locked history for one chain from DefiLlama's own series, downsampled to the window you ask for — the trend line, not a snapshot.' It distinguishes itself clearly from a snapshot tool (market_llama_price_snapshot) and from chain_tvl (which is a sibling point-in-time TVL tool).

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?

The description implies when to use it: when you want a historical TVL trend series rather than a snapshot. It names the data source (DefiLlama's own series) and mentions cost and byte-identical REST equivalence. It doesn't explicitly exclude alternatives or state when not to use it, but the trend-vs-snapshot contrast gives clear context.

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