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

Annotations already mark the tool as read-only, idempotent, and non-destructive. The description adds substantial behavioral context beyond those hints: cost of $0.005 USDC via x402 on Base, unpaid calls returning a payment challenge, no data being never settled, and unknown slugs returning an honest not_found. This is highly valuable for an agent to avoid surprise billing and understand failure semantics.

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?

The description is four sentences with no filler: it states what the tool returns, when to use it, how billing and errors behave, and the equivalent HTTP route. Every sentence adds distinct, decision-relevant information, and the most critical usage guidance appears early.

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?

Despite having no output schema, the description compensates by enumerating the returned fields and covering billing, payment challenge behavior, no-data settlement, and unknown-slug handling. For a single-parameter read-only lookup, this gives an agent everything needed to call it and interpret the result.

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?

The schema already fully documents the single parameter 'slug' with an example, so coverage is 100%. The description reinforces that slug is the lookup key and describes what happens for unknown slugs, but it does not add new format or syntax guidance beyond what the schema provides. Baseline of 3 is appropriate given full schema coverage.

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 operation: it returns 'Full DefiLlama detail for one protocol by slug' and enumerates the response fields (current TVL, per-chain breakdown, category, token symbol, chain list, description, links). It also distinguishes itself from the sibling defi_protocols by emphasizing the singular 'one protocol' and 'after finding a slug with the protocols list'.

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 explicitly says 'Use it after finding a slug with the protocols list', which gives clear sequencing and directs agents to first obtain a slug. It does not name defi_protocols as the alternative tool explicitly, but 'protocols list' is recognizable enough. It could be stronger with an explicit when-not-to-use statement.

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