There are mystical items called Landtool that the ruler of Harappa Land, a land of robots, has instructed his people to find. Two of them, Robotack and Kamerock arrive in Yumegaoka and make friends with detective Kaoru Sugi and his nephew Kakeru. The two join Sugi's agency in their quest to find the Landtool and also solve crimes in their small town. At the same time, they must thwart the Gold Platinum P.D. Agency, headed by Robotack's brother and arch-enemy Torabolt, from finding and profiteering from the Landtool.
Tetsuwan Tantei Robotack provides examples of:
- Affably Evil: Darkrow and Kabados. Although they're out to steal the Land Tool and sell it for money, they're pretty friendly robots all things considered.
- Animal Motifs: Each of the Harappa Robots is themed after a different animal.
- Canon Discontinuity: While the series was listed in one of the Super Hero Taisen specials, said list also included Moerro!! Robocon, which is definitely not a Metal Heroes series, so it was likely referring to series that had come out during the period of time that Kamen Rider was on hiatusnote ; later, Super Hero Taisen Z showed a list of the Metal Heroes series, with Kabutack and Robotack both being absent from said list; additionally, these 2 are the only series that have not received DVD re-releases.
- Crossover: The cast of Robotack meets the cast of B-Robo Kabutack in a crossover special.
- Disney Death: Robotack dies in the final episode, but he eventually survives.
- Heroic Sacrifice: Robotack finally vanquishes the forces of evil in the final episode, but at the cost of his life. Or so it seemed.
- Knight of Cerebus: Torabolt proves himself to be this as soon as he shows up. Within a single episode he defeats Robotack, wins the Shoobidoo Badge competition and steals the Land Tool for himself. Even if he has his eccentricities he's definitely more competent than the other villains in the series (and the Space Mafia).
- Pun-Based Title: Although Tetsuwan is an actual Japanese word, Wan is also the Japanese sound of a dog barking.
- Robot Dog: Robotack is a dog-themed robot.
- Show Within a Show: The first episode has Kaoru watching B-Robo Kabutack, which has interesting implications for when Robotack actually meets Kabutack in a crossover.
- Spoiler Title: Take a wild guess what happens in the last episode, Robotack's Death at Sea. Subverted due to Disney Death.
- Super Mode: Special Mode, which each of the Harappa Robots assumes when there's a need for action or combat.
- Tagalong Kid: Kakeru and his kid detective friends, who help Robotack in figuring out the clues that lead to the next Mineral Macguffin.
- Your Princess Is in Another Castle!: As with Kabutack before it, in most episodes when our protagonists think they've gotten the macguffin, it'll turn out there's another macguffin they need to collect.