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

No annotations are provided, so description bears full burden. It discloses the paid nature ($0.02 via x402) and the data depth limitation ('archive is days old and depth varies by dataset'). However, it does not explicitly state that the tool is read-only or non-destructive, though 'history' implies read. It could mention that there are no side effects, but the payment note and data depth are significant. Score 4, not 5, because it omits the safety profile.

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 a single paragraph, but it is front-loaded with the key purpose and payment info. It is concise and each sentence adds value, though it could be broken into bullet points for readability. It is not overly long and is efficient, so 4.

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?

Given the absence of output schema, the completeness of the dataset and that the 'key' and the description, it is not providing a full picture. The description covers the purpose, usage, and limitations, but it does not specify the return format or pagination. However, the archive is of the return format, but for a single series, it may be acceptable. 4 is possible. The description is reasonably complete, but it does not describe the exact shape of the output, which is a gap.

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 0 movement захранения, with 0% coverage, so the description must compensate. The description explains that 'dataset and key exactly as returned by anansi_search' and that 'since' is a unix timestamp, adding meaning beyond the raw schema. The description also clarifies the 'since' parameter's semantics but does not explain all parameters, but on the 'payment_header' but not full semantics for 'since' and 'dataset' beyond the pointer to search, which is helpful. is 4 is appropriate given the 0% coverage, the description covers many of the basic coverage is that the 'key', so the description provides essential. This is well for the extra. The descriptions of the parameters, including the form of the parameter. The parameters are not provided to have a role, but the description's contribution is significant.

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 clearly states the tool returns a time-series for one key in one dataset, oldest to newest, with timestamps. It distinguishes from siblings like anansi_data_latest, which returns all keys for one moment, and anansi_data_search. The verb is specific: 'chart or backtest a single series'.

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?

Explicitly says when to use (charting/backtesting a single series) and when not to use (comparing many keys at once, pointing to anansi_data_latest). It also warns against expecting history predating the archive. This is textbook usage guidance.

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