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

Annotations already declare readOnlyHint, openWorldHint and destructiveHint=false, so safety is covered structurally. The description adds meaningful context beyond that: the forecast horizon (1-4h), the presence of a calibrated confidence score, an RBF-viability flag, and the external data source (mempool.space), which explains the openWorldHint. It does not discuss failure modes or rate limits.

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 definition is front-loaded with the tool's identity and then lists its outputs in a single dense sentence, with the positioning line last. Every clause carries information, though the output enumeration is long enough that some trimming is conceivable.

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 compensates by enumerating the return fields, and annotations cover the read-only/open-world safety profile. Both parameters are documented in the schema, and the external data source is disclosed. Only the absence of any guidance on data freshness or failure handling keeps it from being fully complete.

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 both parameters (hours_ahead, target_sat_vb) are already fully documented with ranges, defaults and semantics. The description adds no syntax or behavioral detail about them, and its "next 1-4h" phrasing is slightly narrower than the schema's 1-6h range, though not contradictory. Baseline 3 is appropriate when the schema does the heavy lifting.

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 opens with a specific domain and resource ("Bitcoin transaction timing intelligence") and enumerates exactly what it returns — congestion forecast, send window, fee trajectory, confirmation targets, RBF flag — so an agent knows precisely what this tool produces. It implicitly positions itself against raw fee tools ("a synthesis layer above raw fee data") but never names the closest sibling, btc_send_decision, leaving that distinction to inference.

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?

It gives a clear use context — "the decision an autonomous payment agent needs before broadcasting" — which tells the agent when this tool fits in a payment workflow. It stops short of explicit exclusions or naming alternatives (e.g. when to prefer btc_send_decision or btc_price instead), so the routing guidance is contextual rather than directive.

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