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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so safety is covered; the description adds the auth note ('No API key needed') and, with no output schema present, carries the burden of disclosing what comes back: category, related markets, per-plan series counts, and lanes. It does not mention ordering, pagination, or overall result size, which would matter for a full catalog listing.

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?

Two sentences, front-loaded with the resource and scope, with the sibling hand-off placed last where an agent looks for next steps. The middle enumeration of returned fields is long but each item is substantive rather than filler.

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 parameters and no output schema, the description does the necessary work of describing the return shape and the follow-up call, which is sufficient for a simple catalog endpoint. Minor gaps: 'lanes' is undefined jargon, and nothing is said about result ordering or size for what is presumably a large listing.

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 tool takes zero parameters, so there is nothing to disambiguate and the baseline applies. The description's mention of `id` correctly clarifies that the identifier is an *output* field consumed by `tilla_market`, not an input here.

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 names a specific resource (every market TILLA carries) and enumerates the coverage (crypto, US stocks and ETFs, FX, macro) plus the metadata returned per market (category, related markets, series per plan, lanes). It also explicitly routes to the sibling `tilla_market` for single-market lookup, so an agent can distinguish the two without opening either schema.

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 concrete usage pattern — take the `id` from this listing and pass it to `tilla_market` — which is exactly the workflow an agent needs. The 'No API key needed' line removes an authentication prerequisite. It stops short of stating when this listing is *not* the right entry point (e.g. vs `tilla_latest` or `tilla_tiers`), so no explicit exclusions.

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