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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the safety profile is covered. The description adds genuine behavioral context beyond that: how a circle converts into a group chat when enough people join, and the privacy rule 'shows how many joined, never who.' It does not cover pagination or result limits, but that is minor against the annotation coverage.

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?

Front-loads what a circle is, then usage, then routing, in a compact block. The two inline examples consume space but earn it by making the abstract concept ('open circle') concrete; slightly dense, but no filler sentences.

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?

An output schema exists, so return structure is not the description's burden, yet it still volunteers the socially important 'how many joined, never who' detail. For a zero-required-parameter, read-only discovery tool with four documented params, this is nearly complete; only edge cases like empty results or radius behavior are unaddressed.

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 75% with self-documenting descriptions on near, activity and radius_km, plus an enum on lang. 'Search by place and/or activity' restates the schema rather than clarifying formats, defaults, or how radius_km interacts with the person's stored setting. Baseline 3 is appropriate when the schema carries most of the load.

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 concrete verb and resource ('Find open circles — public invitations') and grounds it with two realistic examples showing the shape of a result. It explicitly distinguishes itself from the sibling find_people, so an agent can pick between them 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?

Names the alternative tool and the condition that selects this one: 'Use this before find_people when the person wants to DO something with others.' That is decision-relevant routing, though there is no explicit when-not case (e.g. when the person wants one-on-one connection, use find_people) beyond the implied contrast.

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