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

With no annotations provided, the description carries the full transparency burden and handles it well. It discloses the idempotent-ish behavior ('extra calls same day just add more lines, the streak counts distinct days'), the authentication prerequisite, and the return value ('updated streak and public url'). This gives an agent meaningful behavioral expectations beyond the raw schema.

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 two tight sentences with no filler. The core action is front-loaded, followed by the key usage caveat, prerequisite, and return information. Every sentence earns its place.

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?

For a simple 3-parameter tool with no output schema, the description is complete: it explains when to call it, what prerequisite token is needed, what happens on repeated calls, and what will be returned. The agent has enough context to invoke it correctly and interpret the result.

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 100%, so the schema fully documents all three parameters. The description adds a small amount of context by tying api_token to start_streak and referring to the 'line' concept, but it does not substantially expand on what the schema already provides. Baseline 3 is appropriate.

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 opens with a specific verb and resource: 'Log today's line to keep the streak alive.' It clearly describes what the tool does and is distinguishable from siblings: start_streak creates the streak/token and get_streak presumably reads it, while log_today records today's entry. The return behavior ('updated streak and public url') further confirms the purpose.

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?

The description gives clear usage context: 'Call once per day' and 'Requires the api_token from start_streak,' which establishes the expected workflow and sequencing relative to the sibling tool. It stops short of explicitly naming alternatives or stating when not to use this tool, though the daily-call directive makes the intended usage fairly unambiguous.

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