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

Annotations already cover readOnlyHint and openWorldHint, so the safety profile is given; the description adds genuinely new behavioral context by disclosing the $0.004 USDC per-call x402 cost, which an agent must know before invoking. It does not cover rate limits, payment failure handling, or pagination behavior, so it is not a 5.

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?

A single dense sentence, front-loaded with the resource and scope, then capabilities, then cost. Nothing is redundant, though the stacked parentheticals make it slightly harder to scan and the cost clause could stand alone.

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 carries the return-shape burden and does so by naming observations plus title, units and notes. For a 6-parameter paid read tool the remaining gaps are the default/limit behavior and the mechanics of the x402 payment, which are minor but not zero.

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 83% (baseline 3), and the description earns above baseline by translating the opaque unit codes into plain English (change, % change, % change from a year ago) and explaining that frequency drives aggregation and that start/end define the date range. That is real meaning beyond the schema's terse 'lin, chg, ch1...' and 'd, w, m, q, a' enumerations.

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: fetch any FRED time series by id, with concrete example ids (UNRATE, CPIAUCSL, GDP, DGS10) that make the resource unmistakable. It stops short of naming fred_search, the obvious sibling for discovery-vs-retrieval, so the agent must infer the split from 'by id'.

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?

'by id' implies you must already know the series id, which weakly routes an agent toward fred_search when it does not. There is no explicit when-to-use/when-not statement and no alternative tool is named, so usage is implied rather than specified.

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