start_study

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

With no annotations, the description carries the full burden and does well: it discloses the persistence side effect (timestamp stored on disk), the auth prerequisite (RuntimeError if YPT credentials are not configured), and the returned started_at value. It does not cover idempotency or behavior when a session is already active, so it falls short of fully transparent.

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 purpose is front-loaded in the first sentence and the supporting detail is well organized. The reST :param:/:type:/:rtype: lines are somewhat verbose and partially redundant for an agent reader, but nothing is wasted.

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 values needn't be restated, yet the description still names started_at and the raises condition. Combined with auth, persistence, and both parameters documented, an agent has everything needed to call this correctly.

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%, so the description must compensate, and it does: subject gets a concrete example ('Матеша'), and device_model is explained as reported to the YPT API with its default. This is meaningful beyond the raw schema, though default values are already present in the schema.

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 first sentence states a specific verb and resource ('Start studying a subject') plus the side effect ('record the session start time'). It is immediately distinguishable from the sibling stop_study, which it also references, so an agent can tell the two apart without opening a 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?

Usage is implied (begin a study session), and the description notes that stop_study can be called without arguments because the timestamp is persisted, which hints at the start/stop pairing. However, it never states explicitly when to use this versus get_day_log or what happens if a session is already running, so guidance is only implied rather than stated.

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